COVER - shares	9 Months Ended
COVER - shares	Sep. 30, 2019	Oct. 24, 2019
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	001-14195
Entity Registrant Name	AMERICAN TOWER CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	65-0723837
Entity Address, Address Line One	116 Huntington Avenue
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02116
City Area Code	617
Local Phone Number	375-7500
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		442,940,435
Entity Central Index Key	0001053507
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	AMT
Security Exchange Name	NYSE
1.375% Senior Notes due 2025
Document Information [Line Items]
Title of 12(b) Security	1.375% Senior Notes due 2025
Trading Symbol	AMT 25A
Security Exchange Name	NYSE
1.950% Senior Notes due 2026
Document Information [Line Items]
Title of 12(b) Security	1.950% Senior Notes due 2026
Trading Symbol	AMT 26B
Security Exchange Name	NYSE

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 1,352.6	$ 1,208.7
Restricted cash	95.7	96.2
Accounts receivable, net	441.7	459.0
Prepaid and other current assets	472.0	621.2
Total current assets	2,362.0	2,385.1
PROPERTY AND EQUIPMENT, net	11,283.2	11,247.1
GOODWILL	5,481.4	5,501.9
OTHER INTANGIBLE ASSETS, net	10,895.8	11,174.3
DEFERRED TAX ASSET	143.5	157.7
DEFERRED RENT ASSET	1,677.7	1,581.7
RIGHT-OF-USE ASSET	7,214.7
NOTES RECEIVABLE AND OTHER NON-CURRENT ASSETS	248.9	962.6
TOTAL	39,307.2	33,010.4
CURRENT LIABILITIES:
Accounts payable	136.2	130.8
Accrued expenses	856.7	948.3
Distributions payable	427.5	377.4
Accrued interest	145.4	174.5
Current portion of operating lease liability	475.1
Current portion of long-term obligations	2,443.6	2,754.8
Unearned revenue	302.9	304.1
Total current liabilities	4,787.4	4,689.9
LONG-TERM OBLIGATIONS	19,040.0	18,405.1
OPERATING LEASE LIABILITY	6,448.0
ASSET RETIREMENT OBLIGATIONS	1,252.5	1,210.0
DEFERRED TAX LIABILITY	538.5	535.9
OTHER NON-CURRENT LIABILITIES	870.9	1,265.1
Total liabilities	32,937.3	26,106.0
COMMITMENTS AND CONTINGENCIES
REDEEMABLE NONCONTROLLING INTERESTS	574.8	1,004.8
EQUITY (shares in thousands):
Common stock: $.01 par value; 1,000,000 shares authorized; 453,392 and 451,617 shares issued; and 442,835 and 441,060 shares outstanding, respectively	4.5	4.5
Additional paid-in capital	10,551.8	10,380.8
Distributions in excess of earnings	(1,130.1)	(1,199.5)
Accumulated other comprehensive loss	(2,979.0)	(2,642.9)
Treasury stock (10,557 shares at cost)	(1,206.8)	(1,206.8)
Total American Tower Corporation equity	5,240.4	5,336.1
Noncontrolling interests	554.7	563.5
Total equity	5,795.1	5,899.6
TOTAL	$ 39,307.2	$ 33,010.4

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, shares issued (in shares)	453,392,000	451,617,000
Common stock, shares outstanding (in shares)	442,386,000	441,060,000
Treasury stock, shares (in shares)	10,557,000	10,557,000

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
REVENUES:
Revenue from contract with customer	$ 137.3	$ 121.9	$ 402.8	$ 365.1
Total operating revenues	1,953.6	1,785.5	5,656.6	5,308.2
Costs of operations (exclusive of items shown separately below):
Property	548.0	543.1	1,630.4	1,597.7
Services	11.9	13.6	36.2	39.2
Depreciation, amortization and accretion	442.8	448.9	1,328.6	1,344.9
Selling, general, administrative and development expense	187.9	177.9	550.8	540.7
Other operating expenses	34.7	34.8	83.5	269.6
Total operating expenses	1,225.3	1,218.3	3,629.5	3,792.1
OPERATING INCOME	728.3	567.2	2,027.1	1,516.1
OTHER INCOME (EXPENSE):
Interest income (expense), TV Azteca	0.0	0.6	0.0	(0.1)
Interest income	12.2	10.1	36.3	43.9
Interest expense	(201.3)	(209.2)	(613.3)	(616.7)
Loss on retirement of long-term obligations	0.0	0.0	(22.2)	0.0
Other income (including foreign currency (losses) gains of ($1.1), $2.2, $13.7 and ($14.9), respectively)	2.8	21.1	19.6	14.1
Total other expense	(186.3)	(177.4)	(579.6)	(558.8)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	542.0	389.8	1,447.5	957.3
Income tax (provision) benefit	(36.7)	(12.5)	(100.3)	14.7
NET INCOME	505.3	377.3	1,347.2	972.0
Net income attributable to noncontrolling interests	(6.7)	(10.4)	(22.1)	(13.2)
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION STOCKHOLDERS	498.6	366.9	1,325.1	958.8
Dividends on preferred stock	0.0	0.0	0.0	(9.4)
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION COMMON STOCKHOLDERS	$ 498.6	$ 366.9	$ 1,325.1	$ 949.4
NET INCOME PER COMMON SHARE AMOUNTS:
Basic net income attributable to American Tower Corporation common stockholders (in dollars per share)	$ 1.13	$ 0.83	$ 3.00	$ 2.16
Diluted net income attributable to American Tower Corporation common stockholders (in dollars per share)	$ 1.12	$ 0.83	$ 2.98	$ 2.15
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING (in thousands):
BASIC (in shares)	442,763	440,889	442,110	439,191
DILUTED (in shares)	445,829	444,121	445,352	442,468
Property Revenue [Member]
REVENUES:
Total operating revenues	$ 1,921.6	$ 1,751.6	$ 5,556.5	$ 5,211.4
Services revenue
REVENUES:
Revenue from contract with customer	$ 32.0	$ 33.9	$ 100.1	$ 96.8

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 505.3	$ 377.3	$ 1,347.2	$ 972.0
Other comprehensive income (loss):
Changes in fair value of cash flow hedges, each net of tax expense of $0	0.0	0.0	(0.1)	0.0
Reclassification of unrealized losses on cash flow hedges to net income, each net of tax expense of $0	0.1	(0.0)	0.2	0.2
Adjustment to redeemable noncontrolling interest	0.0	0.0	0.0	78.8
Purchase of noncontrolling interest	0.0	0.0	0.0	0.5
Foreign currency translation adjustments, net of tax (benefit) expense of ($0.0), $1.0, $0.4 and ($2.8), respectively	(407.6)	(248.5)	(320.6)	(957.1)
Other comprehensive loss	(407.5)	(248.5)	(320.5)	(877.6)
Comprehensive income	97.8	128.8	1,026.7	94.4
Allocation of accumulated other comprehensive income resulting from purchase of redeemable noncontrolling interest	0.0	0.0	(52.4)	0.0
Comprehensive loss attributable to noncontrolling interests	28.5	51.9	14.7	146.4
Comprehensive income attributable to American Tower Corporation stockholders	$ 126.3	$ 180.7	$ 989.0	$ 240.8

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Changes in fair value of cash flow hedges, tax	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Reclassification of unrealized gains on cash flow hedges to net income, tax	0.0	0.0	0.0	0.0
Foreign currency translation adjustments, tax expense (benefit)	$ 0.0	$ 1.0	$ 0.4	$ (2.8)

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 1,347.2	$ 972.0
Adjustments to reconcile net income to cash provided by operating activities
Depreciation, amortization and accretion	1,328.6	1,344.9
Amortization of operating leases	440.1	0.0
Stock-based compensation expense	87.9	111.3
Loss on early retirement of long-term obligations	22.2	0.0
Other non-cash items reflected in statements of operations	163.8	194.5
Increase in net deferred rent balances	(99.6)	(23.9)
Reduction in operating lease liability	(388.9)	0.0
Increase in assets	(84.5)	(143.6)
(Decrease) increase in liabilities	(57.9)	29.9
Cash provided by operating activities	2,758.9	2,485.1
CASH FLOWS FROM INVESTING ACTIVITIES
Payments for purchase of property and equipment and construction activities	(724.6)	(610.4)
Payments for acquisitions, net of cash acquired	(687.6)	(1,437.8)
Proceeds from sale of short-term investments and other non-current assets	378.4	1,097.0
Payments for short-term investments	(355.9)	(1,072.2)
Deposits and other	(11.1)	(31.7)
Cash used for investing activities	(1,400.8)	(2,055.1)
CASH FLOWS FROM FINANCING ACTIVITIES
Borrowings under credit facilities	3,330.0	2,913.3
Proceeds from issuance of senior notes, net	3,529.7	584.9
Proceeds from term loan	1,300.0	1,500.0
Proceeds from issuance of securities in securitization transaction	0.0	500.0
Repayments of notes payable, credit facilities, senior notes, secured debt, term loan, finance leases and capital leases	(7,672.4)	(4,329.2)
Distributions to noncontrolling interest holders, net	(11.6)	(14.3)
Purchases of common stock	0.0	(181.2)
Proceeds from stock options and employee stock purchase plan	92.7	54.1
Distributions paid on common stock	(1,182.2)	(975.1)
Distributions paid on preferred stock	0.0	(18.9)
Payment for early retirement of long-term obligations	(21.0)	0.0
Deferred financing costs and other financing activities	(114.1)	(47.4)
Purchase of redeemable noncontrolling interest	(425.7)	0.0
Purchase of noncontrolling interest	0.0	(20.5)
Cash used for financing activities	(1,174.6)	(34.3)
Net effect of changes in foreign currency exchange rates on cash and cash equivalents, and restricted cash	(40.1)	(57.3)
NET INCREASE IN CASH AND CASH EQUIVALENTS, AND RESTRICTED CASH	143.4	338.4
CASH AND CASH EQUIVALENTS, AND RESTRICTED CASH, BEGINNING OF PERIOD	1,304.9	954.9
CASH AND CASH EQUIVALENTS, AND RESTRICTED CASH, END OF PERIOD	1,448.3	1,293.3
CASH PAID FOR INCOME TAXES (NET OF REFUNDS OF $9.5 AND $24.9, RESPECTIVELY)	111.0	75.3
CASH PAID FOR INTEREST	621.5	640.8
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Decrease in accounts payable and accrued expenses for purchases of property and equipment and construction activities	(30.5)	(22.9)
Purchases of property and equipment under finance leases, perpetual easements and capital leases	52.8	39.4
Acquisition of Commercialization Rights	$ 0.0	$ 24.8

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Millions	Total	Preferred Stock Preferred Stock - Series B Convertible Preferred Stock Subject to Mandatory Redemption	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Distributions in Excess of Earnings	Noncontrolling Interests
BALANCE (shares) at Dec. 31, 2017		1,375,000	437,729,000	(8,909,000)
BALANCE at Dec. 31, 2017	$ 6,828.1	$ 0.0	$ 4.4	$ (974.0)	$ 10,247.5	$ (1,978.3)	$ (1,058.1)	$ 586.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation related activity (shares)			1,236,000
Stock-based compensation related activity	124.5		$ 0.0		124.5
Issuance of common stock- stock purchase plan (shares)			45,000
Issuance of common stock- stock purchase plan	5.3		$ 0.0		5.3
Conversion of preferred stock (shares)		(1,375,000)	12,020,000
Conversion of preferred stock	0.0	$ 0.0	$ 0.1		(0.1)
Treasury stock activity (shares)				(1,346,000)
Treasury stock activity	(189.2)			$ (189.2)
Changes in fair value of cash flow hedges, net of tax	0.0					0.0
Reclassification of unrealized losses on cash flow hedges to net income, net of tax	0.2					0.2
Foreign currency translation adjustment, net of tax	(827.6)					(797.5)		(30.1)
Adjustment to redeemable noncontrolling interest	28.1				(50.7)	78.8
Distributions to noncontrolling interest	(1.0)							(1.0)
Purchase of redeemable noncontrolling interest	(20.5)				(16.5)	0.5		(4.5)
Common stock distributions declared	(1,024.5)						(1,024.5)
Preferred stock dividends declared	(18.9)						(18.9)
Net income	985.8						958.8	27.0
BALANCE (shares) at Sep. 30, 2018		0	451,030,000	(10,255,000)
BALANCE at Sep. 30, 2018	5,928.7	$ 0.0	$ 4.5	$ (1,163.2)	10,310.0	(2,696.3)	(1,104.3)	578.0
BALANCE (shares) at Jun. 30, 2018			450,817,000	(9,631,000)
BALANCE at Jun. 30, 2018	6,126.6		$ 4.5	$ (1,074.0)	10,251.9	(2,510.1)	(1,121.6)	575.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation related activity (shares)			213,000
Stock-based compensation related activity	58.1		$ 0.0		58.1
Treasury stock activity (shares)				(624,000)
Treasury stock activity	(89.2)			$ (89.2)
Changes in fair value of cash flow hedges, net of tax	0.0					0.0
Reclassification of unrealized losses on cash flow hedges to net income, net of tax	(0.0)					(0.0)
Foreign currency translation adjustment, net of tax	(192.5)					(186.2)		(6.3)
Distributions to noncontrolling interest	(0.5)							(0.5)
Common stock distributions declared	(349.6)						(349.6)
Net income	375.8						366.9	8.9
BALANCE (shares) at Sep. 30, 2018		0	451,030,000	(10,255,000)
BALANCE at Sep. 30, 2018	5,928.7	$ 0.0	$ 4.5	$ (1,163.2)	10,310.0	(2,696.3)	(1,104.3)	578.0
BALANCE (shares) at Dec. 31, 2018		0	451,617,000	(10,557,000)
BALANCE at Dec. 31, 2018	5,899.6	$ 0.0	$ 4.5	$ (1,206.8)	10,380.8	(2,642.9)	(1,199.5)	563.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation related activity (shares)			1,734,000
Stock-based compensation related activity	112.9		$ 0.0		112.9
Issuance of common stock- stock purchase plan (shares)			41,000
Issuance of common stock- stock purchase plan	$ 5.7		$ 0.0		5.7
Treasury stock activity (shares)	0
Changes in fair value of cash flow hedges, net of tax	$ (0.1)					(0.1)
Reclassification of unrealized losses on cash flow hedges to net income, net of tax	0.2					0.2
Foreign currency translation adjustment, net of tax	(316.3)					(283.8)		(32.5)
Contributions from noncontrolling interest	2.7							2.7
Distributions to noncontrolling interest	(1.1)							(1.1)
Purchase of redeemable noncontrolling interest	0.0				52.4	(52.4)
Common stock distributions declared	(1,231.0)						(1,231.0)
Net income	1,347.2						1,325.1	22.1
BALANCE (shares) at Sep. 30, 2019		0	453,392,000	(10,557,000)
BALANCE at Sep. 30, 2019	5,795.1	$ 0.0	$ 4.5	$ (1,206.8)	10,551.8	(2,979.0)	(1,130.1)	554.7
BALANCE (shares) at Jun. 30, 2019			452,943,000	(10,557,000)
BALANCE at Jun. 30, 2019	6,043.1		$ 4.5	$ (1,206.8)	10,492.7	(2,606.7)	(1,206.2)	565.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation related activity (shares)			449,000
Stock-based compensation related activity	59.1		$ 0.0		59.1
Changes in fair value of cash flow hedges, net of tax	0.0					0.0
Reclassification of unrealized losses on cash flow hedges to net income, net of tax	0.1					0.1
Foreign currency translation adjustment, net of tax	(392.2)					(372.4)		(19.8)
Contributions from noncontrolling interest	2.7							2.7
Distributions to noncontrolling interest	(0.5)							(0.5)
Common stock distributions declared	(422.5)						(422.5)
Net income	505.3						498.6	6.7
BALANCE (shares) at Sep. 30, 2019		0	453,392,000	(10,557,000)
BALANCE at Sep. 30, 2019	$ 5,795.1	$ 0.0	$ 4.5	$ (1,206.8)	$ 10,551.8	$ (2,979.0)	$ (1,130.1)	$ 554.7

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES

9 Months Ended

Sep. 30, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES

The accompanying consolidated and condensed consolidated financial statements have been prepared by American Tower Corporation (together with its subsidiaries, “ATC” or the “Company”) pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The financial information included herein is unaudited. However, the Company believes that all adjustments, which are of a normal and recurring nature, considered necessary for a fair presentation of its financial position and results of operations for such periods have been included herein. The consolidated and condensed consolidated financial statements and related notes should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 (the “2018 Form 10-K”). The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of the results that may be expected for the entire year.

Principles of Consolidation and Basis of Presentation—The accompanying consolidated and condensed consolidated financial statements include the accounts of the Company and those entities in which it has a controlling interest. Investments in entities that the Company does not control are accounted for using the equity method or as investments in equity securities, depending upon the Company’s ability to exercise significant influence over operating and financial policies. All intercompany accounts and transactions have been eliminated. As of September 30, 2019, the Company holds (i) a 51% controlling interest in each of two joint ventures, one in Ghana and one in Uganda (MTN Group Limited (“MTN”) holds a 49% noncontrolling interest), (ii) a 51% controlling interest in a joint venture that primarily consists of the Company’s operations in Germany and France (PGGM holds a 49% noncontrolling interest), (iii) an approximate 81% controlling interest in a subsidiary of the Company in South Africa (South African investors hold an approximate 19% noncontrolling interest) and (iv) a 79% controlling interest in ATC Telecom Infrastructure Private Limited (“ATC TIPL”), formerly Viom Networks Limited (“Viom”), in India.

Significant Accounting Policies—The Company’s significant accounting policies are described in note 1 to the Company’s consolidated financial statements included in the 2018 Form 10-K. There have been no material changes to the Company’s significant accounting policies during the nine months ended September 30, 2019, except the adoption of new lease accounting guidance, as discussed below.

Cash and Cash Equivalents and Restricted Cash—The reconciliation of cash and cash equivalents and restricted cash reported within the applicable balance sheet that sum to the total of the same such amounts shown in the statement of cash flows is as follows:



	Nine Months Ended September 30,
	2019		2018
Cash and cash equivalents	$	1,352.6	$	1,026.5
Restricted cash	95.7		266.8
Total cash and cash equivalents and restricted cash	$	1,448.3	$	1,293.3

Lease—The new lease standard requires leases to be accounted for using a right-of-use model, which recognizes that, at the date of commencement, a lessee has a financial obligation to make lease payments to the lessor for the right to use the underlying asset during the lease term. The lessee recognizes a corresponding right-of-use asset related to this right.

On January 1, 2019, the Company elected to adopt the new lease standard using the modified retrospective method applied to lease arrangements that were in place on the transition date. Results for reporting periods beginning January 1, 2019 are presented under the new standard, while prior-period amounts are not adjusted and continue to be reported in accordance with accounting under the previously applicable guidance.

The Company elected certain available practical expedients which permit the adopter to not reassess certain items upon adoption, including: (i) whether any existing contracts are or contain leases, (ii) the classification of existing leases and (iii) initial direct costs for existing leases. The Company also elected the practical expedient related to easements, which permits carryforward accounting treatment for land easements on existing agreements.

The Company recorded a net increase to opening Distributions in excess of earnings in its consolidated balance sheet of $24.7 million as of January 1, 2019 due to the cumulative impact of adopting the new lease standard. This adjustment related to right-of-use asset impairments. The Company also recorded a lease liability of $6.9 billion and a corresponding right-of-use asset of $7.1 billion upon adoption of the new lease standard. Those rights and obligations are primarily related to operating leases for ground space underneath the Company’s communications sites. The right-of-use assets recorded include, among other items, amounts previously classified as prepaid rent, deferred lease acquisition costs, fair value adjustments on acquired leases and long-term deferred rent obligations. Finance leases, which primarily relate to towers, equipment and vehicles, were largely unchanged. There was no significant change to the Company’s consolidated statements of operations resulting from the adoption of this standard.

The Company did not elect the practical expedient for short-term leases, which permits an adopter to not apply the lease standard to leases with a remaining maturity of one year or less, and applied the new lease accounting standard to all leases, including short-term leases.

In conjunction with the adoption of the new lease accounting guidance, the Company applied the lessor and lessee practical expedient and no longer separates lease and non-lease components within a lease agreement when the timing and pattern of revenue recognition for the components are the same and the combined single lease component is classified as an operating lease. Certain amounts, such as power and fuel and common area maintenance, which were previously reported as non-lease revenue, are now accounted for as lease revenue. Accordingly, the Company has reclassified certain prior-period amounts within its disclosures.

Revenue—Most of the Company’s revenue is derived from leasing arrangements and is accounted for as lease revenue unless the timing and pattern of revenue recognition differs from the lease components. Revenue related to distributed antenna system (“DAS”) networks and fiber results from agreements with tenants that are not leases.

Non-lease revenue—Non-lease revenue consists primarily of revenue generated from DAS networks, fiber and other property related revenue. DAS networks and fiber arrangements require that the Company provide the tenant the right to use the applicable communications infrastructure. Performance obligations are satisfied over time for the duration of the arrangements. Other property related revenue streams, which include site inspections, are not material on either an individual or consolidated basis.

Services revenue—The Company offers tower-related services in the United States. These services include site acquisition, zoning and permitting (“AZP”) and structural analysis. There is a single performance obligation related to AZP and revenue is recognized over time based on milestones achieved, which are determined based on costs expected to be incurred. Structural analysis services may have more than one performance obligation, contingent upon the number of contracted services. Revenue is recognized at the point in time the services are completed.

A summary of revenue disaggregated by source and geography is as follows:



Three Months Ended September 30, 2019	U.S.		Asia		EMEA		Latin America		Total
Non-lease property revenue	$	66.7	$	2.2	$	2.3	$	34.1	$	105.3
Services revenue	32.0		—		—		—		32.0
Total non-lease revenue	$	98.7	$	2.2	$	2.3	$	34.1	$	137.3
Property lease revenue	1,029.2		310.3		179.2		297.6		1,816.3
Total revenue	$	1,127.9	$	312.5	$	181.5	$	331.7	$	1,953.6



Three Months Ended September 30, 2018 (1)	U.S.		Asia		EMEA		Latin America		Total
Non-lease property revenue	$	62.4	$	1.6	$	0.4	$	23.6	$	88.0
Services revenue	33.9		—		—		—		33.9
Total non-lease revenue	$	96.3	$	1.6	$	0.4	$	23.6	$	121.9
Property lease revenue	895.3		321.5		166.2		280.6		1,663.6
Total revenue	$	991.6	$	323.1	$	166.6	$	304.2	$	1,785.5

_______________


(1)	Prior-period amounts adjusted with the adoption of the new lease accounting guidance, as applicable.



Nine Months Ended September 30, 2019	U.S.		Asia		EMEA		Latin America		Total
Non-lease property revenue	$	186.3	$	6.7	$	5.8	$	103.9	$	302.7
Services revenue	100.1		—		—		—		100.1
Total non-lease revenue	$	286.4	$	6.7	$	5.8	$	103.9	$	402.8
Property lease revenue	2,903.1		915.8		528.2		906.7		5,253.8
Total revenue	$	3,189.5	$	922.5	$	534.0	$	1,010.6	$	5,656.6



Nine Months Ended September 30, 2018 (1)	U.S.		Asia		EMEA		Latin America		Total
Non-lease property revenue	$	190.3	$	5.0	$	1.1	$	71.9	$	268.3
Services revenue	96.8		—		—		—		96.8
Total non-lease revenue	$	287.1	$	5.0	$	1.1	$	71.9	$	365.1
Property lease revenue	2,655.8		899.0		506.4		881.9		4,943.1
Total revenue	$	2,942.9	$	904.0	$	507.5	$	953.8	$	5,308.2

_______________


(1)	Prior-period amounts adjusted with the adoption of the new lease accounting guidance, as applicable.

Information about receivables, contract assets and contract liabilities from non-lease contracts with tenants is as follows:



	September 30, 2019		December 31, 2018 (1)
Accounts receivable	$	94.0	$	92.6
Prepaids and other current assets	10.0		7.7
Notes receivable and other non-current assets	26.0		22.2
Unearned revenue (2)	37.9		35.0
Other non-current liabilities (3)	68.8		54.1

_______________


(1)	Prior-period amounts adjusted with the adoption of the new lease accounting guidance, as applicable.


(2)	Excludes $56.1 million and $55.0 million of capital contributions related to DAS networks as of September 30, 2019 and December 31, 2018, respectively.


(3)	Excludes $301.6 million and $313.6 million of capital contributions related to DAS networks as of September 30, 2019 and December 31, 2018, respectively.

The Company records unearned revenue when payments are received from tenants in advance of the completion of the Company’s performance obligations. Long-term unearned revenue is included in Other non-current liabilities. During the three and nine months ended September 30, 2019, the Company recognized $15.7 million and $45.8 million, respectively, of revenue that was included in the Unearned revenue balance as of December 31, 2018. During the three and nine months ended September 30, 2018, the Company recognized $10.8 million and $33.3 million, respectively, of revenue from the Unearned revenue balance as of January 1, 2018. The Company also recognized revenues

of $14.8 million and $44.2 million during the three and nine months ended September 30, 2019, respectively, and $13.8 million and $41.2 million during the three and nine months ended September 30, 2018, respectively, for capital contributions related to DAS networks. There was $0.1 million and $0.3 million during the three and nine months ended September 30, 2019, respectively, and $0.2 million and $0.4 million during the three and nine months ended September 30, 2018, respectively, of revenue recognized from Other non-current liabilities.

The Company records unbilled receivables, which are included in Prepaids and other current assets, when it has completed a performance obligation prior to its ability to bill under the customer arrangement. Other contract assets are included in Notes receivable and other non-current assets. The Company did not record any change in unbilled receivables attributable to revenue recognized during each of the three and nine months ended September 30, 2019 and 2018. The change in contract assets attributable to revenue recognized was $5.2 million and $3.8 million during the three and nine months ended September 30, 2019, respectively, and less than $0.1 million for each of the three and nine months ended September 30, 2018.

Accounting Standards Updates

In June 2016, the Financial Accounting Standards Board (the “FASB”) issued guidance that modifies how entities measure credit losses on most financial instruments. The new guidance replaces the current "incurred loss" model with an "expected credit loss" model that requires consideration of a broader range of information to estimate expected credit losses over the lifetime of the asset. The new guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, and will be applied using a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of the effective date. Operating lease receivables are not within the scope of this guidance. The Company is finalizing its analysis of the impact of this guidance on its financial statements and does not expect the adoption of this guidance to have a material impact on the Company’s financial statements.

In January 2017, the FASB issued guidance on accounting for goodwill impairments. The guidance eliminates Step 2 from the goodwill impairment test and requires, among other things, recognition of an impairment loss when the carrying value of a reporting unit exceeds its fair value. The loss recognized is limited to the total amount of goodwill allocated to that reporting unit. The guidance is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company does not expect the adoption of this guidance to have a material impact on the Company’s financial statements.

In August 2018, the FASB issued guidance on the accounting for implementation costs incurred in a cloud computing arrangement that is a service contract. This guidance aligns the accounting for costs incurred to implement a cloud computing arrangement that is a service arrangement with the guidance on capitalizing costs associated with developing or obtaining internal-use software. The Company adopted this guidance prospectively on July 1, 2019. The adoption of this guidance did not have a material impact on the Company’s financial statements.

PROPERTY AND EQUIPMENT

9 Months Ended

Sep. 30, 2019

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT

Property and equipment (including assets held under financing leases) consisted of the following:



	Estimated Useful Lives (years) (1)	As of
	Estimated Useful Lives (years) (1)	September 30, 2019			December 31, 2018
Towers	Up to 20	$	13,044.9		$	12,777.9
Equipment (2)	2 - 20	1,807.1			1,667.3
Buildings and improvements	3 - 32	636.2			628.5
Land and improvements (3)	Up to 20	2,435.4			2,285.4
Construction-in-progress		378.7			358.1
Total		18,302.3			17,717.2
Less accumulated depreciation		(7,019.1		)	(6,470.1		)
Property and equipment, net		$	11,283.2		$	11,247.1

_______________


(1)	Assets on leased land are depreciated over the shorter of the estimated useful life of the asset or the term of the corresponding ground lease taking into consideration lease renewal options and residual value.


(2)	Includes fiber and DAS assets.


(3)	Estimated useful lives apply to improvements only.

Total depreciation expense was $224.7 million and $677.5 million for the three and nine months ended September 30, 2019, respectively, and $221.0 million and $666.9 million for the three and nine months ended September 30, 2018, respectively. Depreciation expense includes amounts related to finance lease assets for the three and nine months ended September 30, 2019 of $42.4 million and $127.4 million, respectively.

As of December 31, 2018, property and equipment included $4,369.5 million of capital lease assets with related equipment and improvements and $1,016.2 million of accumulated depreciation.

Information about finance lease-related balances is as follows:



		As of
Finance leases:	Classification	September 30, 2019
Property and equipment	Towers	$	2,706.9
Accumulated depreciation		(1,039.8		)
Property and equipment, net		$	1,667.1

Property and equipment	Buildings and improvements	$	171.4
Accumulated depreciation		(64.8		)
Property and equipment, net		$	106.6

Property and equipment	Land	$	152.1

Property and equipment	Equipment	$	45.0
Accumulated depreciation		(11.9		)
Property and equipment, net		$	33.1

As of September 30, 2019, the Company had $1,533.3 million of perpetual land easements which are not depreciable.

LEASES

9 Months Ended

Sep. 30, 2019

Leases [Abstract]

LEASES

The Company determines if an arrangement is a lease at the inception of the agreement. The Company considers an arrangement to be a lease if it conveys the right to control the use of the communications site or ground space underneath a communications site for a period of time in exchange for consideration. The Company is both a lessor and a lessee.

Lessor—The Company is a lessor in most of its revenue arrangements, as property revenue is derived from tenant leases of specifically-identified, physically distinct space on the Company’s communications real estate assets. The Company’s lease arrangements with its tenants vary depending upon the region and the industry of the tenant and generally have initial non-cancellable terms of five to ten years with multiple renewal terms. The leases also contain provisions that periodically increase the rent due, typically annually, based on a fixed escalation percentage or an inflationary index, or a combination of both. The Company structures its leases to include financial penalties if a tenant terminates the lease, which serve to disincentivize tenants from terminating the lease prior to the expiration of the lease term.

The Company’s leasing arrangements outside of the U.S. may require that the Company provide power to the communications site through an electrical grid connection, diesel fuel generators or other sources and permit the Company to pass through the costs of, or otherwise charge for, these services. Many arrangements require that the communications site has power for a specified percentage of time. In most cases, if delivery of power falls below the specified service level, a corresponding reduction in revenue is recorded. The Company has determined that this performance obligation is satisfied over time for the duration of the lease.

The Company typically has more than one tenant on a site and, by performing ordinary course repair and maintenance work, can often lease a site, either through renewing existing agreements or leasing to new tenants, for periods beyond the existing tenant lease term. Accordingly, the Company has minimal risk with respect to the residual value of its leased assets. Communications sites are depreciated over their estimated useful lives, which generally do not exceed twenty years.

As of September 30, 2019, the Company does not have any material related party leases as a lessor. The Company generally does not enter into sales-type leases or direct financing leases. The Company’s leases generally do not include any incentives for the lessee and do not include any lessee purchase options.

Historically, the Company has been able to successfully renew its ground leases as needed to ensure continuation of its tower revenue. Accordingly, the Company assumes that it will have access to the land underneath its tower sites when calculating future minimum rental receipts. Future minimum rental receipts expected under non-cancellable operating lease agreements as of September 30, 2019 were as follows:



Fiscal Year	Amount (1)
Remainder of 2019	$	1,394.7
2020	5,645.9
2021	5,442.0
2022	4,846.6
2023	4,710.8
Thereafter	24,225.4
Total	$	46,265.4

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

On August 30, 2019, the Company entered into a new master lease agreement with one of its tenants in the U.S., AT&T Inc. (“AT&T”), which resulted in an additional $13.7 billion in future minimum rental receipts expected under non-cancellable operating lease agreements.

Future minimum rental receipts expected under non-cancellable operating lease agreements in effect at December 31, 2018 were as follows:



Year Ended December 31,	Amount (1)
2019	$	5,251.2
2020	5,062.2
2021	4,676.1
2022	3,754.6
2023	3,457.3
Thereafter	12,641.1
Total	$	34,842.5

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Lessee—The Company enters into arrangements as a lessee primarily for ground space underneath its communications sites. These arrangements are typically long-term lease agreements with initial non-cancellable terms of approximately five to ten years with one or more automatic or exercisable renewal periods and specified increases in lease payments upon exercise of the renewal options. The Company typically exercises its ground lease renewal options in order to provide ongoing tenant space on its communications sites through the end of the tenant lease term. Escalation clauses present in operating leases, excluding those tied to a consumer price index (“CPI”) or other inflation-based indices, are recognized on a straight-line basis over the estimated lease term of the applicable lease. Additionally, the escalations tied to CPI or another inflation-based index are considered variable lease payments. In certain circumstances, the Company enters into revenue sharing arrangements with the ground space owner, which results in variability in lease payments. In most markets outside of the U.S., in the event there are no tenants on the communications site, the Company generally has unilateral termination rights and in certain situations, the lease is structured to allow for termination by the Company with minimal or no penalties. Ground lease arrangements usually include annual escalations and do not contain any residual value guarantees or restrictions on dividends, other financial obligations or other similar terms. The Company has entered into certain transactions whereby at the end of a lease, sublease or similar arrangement, the Company has the option to purchase the corresponding communications sites. These transactions are further described in note 15.

The Company’s lease liability is the present value of the remaining minimum rental payments to be made over the remaining lease term, including renewal options reasonably certain to be exercised. The Company also considers termination options and factors those into the determination of lease payments when appropriate. To determine the lease term, the Company considers all renewal periods that are reasonably certain to be exercised, taking into consideration all economic factors, including the communications site’s estimated economic life (generally 20 years) and the respective lease terms of the Company’s tenants under the existing lease arrangements on such site.

As of the adoption date and new lease inception, the Company’s right-of-use asset is equal to its lease liability, plus payments made prior to the commencement date and initial direct costs, net of any impairment losses, lease incentives, fair value adjustments on acquired leases and deferred rent amount recorded under the prior lease accounting guidance. The Company assesses its right-of-use asset and other lease-related assets for impairment, as described in note 1 to the Company’s consolidated financial statements included in the 2018 Form 10-K. There were no material impairments recorded related to these assets during the three and nine months ended September 30, 2019.

As of September 30, 2019, the Company does not have any material related party leases as a lessee. The Company does not have any sale-leaseback arrangements as lessee and typically does not enter into leveraged leases.

The Company leases certain land and office space under operating leases and land and improvements, towers and vehicles under finance leases. As of September 30, 2019, operating lease assets were included in Right-of-use asset and finance lease assets were included in Property and equipment, net in the consolidated balance sheet.

Information about other lease-related balances as of September 30, 2019 is as follows:



Operating leases:
Right-of-use asset	$	7,214.7

Current portion of lease liability	$	475.1
Lease liability	6,448.0
Total operating lease liability	$	6,923.1

Finance leases:
Current portion of lease liability	$	7.1
Lease liability	23.1
Total finance lease liability	$	30.2

As most of the Company’s leases do not specifically state an implicit rate, the Company uses a market-specific incremental borrowing rate consistent with the lease term as of the lease commencement date when calculating the present value of remaining lease payments. The incremental borrowing rate reflects the cost to borrow on a securitized basis in each market. The remaining lease term does not reflect all renewal options available to the Company, only those renewal options that the Company has assessed as reasonably certain of being exercised taking into consideration the economic factors noted above.

The weighted-average remaining lease terms and incremental borrowing rates as of September 30, 2019 are as follows:



Operating leases:
Weighted-average remaining lease term (years)	13.3
Weighted-average incremental borrowing rate	6.3	%

Finance leases:
Weighted-average remaining lease term (years)	15.0
Weighted-average incremental borrowing rate	6.2	%

The following table sets forth the components of lease cost for the three and nine months ended September 30, 2019:



	Three Months Ended September 30, 2019		Nine Months Ended September 30, 2019
Operating lease cost	$	249.5	$	760.3
Variable lease costs not included in lease liability (1)	67.7		190.8

_______________


(1)	Includes property tax paid on behalf of the landlord.

The interest expense on finance lease liabilities was $0.4 million and $1.1 million for the three and nine months ended September 30, 2019, respectively. Assets held under finance leases are recorded in property and equipment and are depreciated over the lesser of the remaining lease term or the remaining useful life.

Supplemental cash flow information for the nine months ended September 30, 2019 is as follows:



Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	(701.9	)
Operating cash flows from finance leases	$	(1.1	)
Financing cash flows from finance leases	$	(16.4	)

Non-cash items:
New operating leases	$	224.8
Operating lease modifications and reassessments	$	338.9

As of September 30, 2019, the Company does not have material operating or financing leases that have not yet commenced.

Maturities of operating and finance lease liabilities as of September 30, 2019 were as follows:



Fiscal Year	Operating Lease (1)			Finance Lease (1)
Remainder of 2019	$	217.4		$	2.8
2020	876.0			7.6
2021	860.4			4.9
2022	822.4			4.0
2023	785.4			2.6
Thereafter	6,735.8			45.5
Total lease payments	10,297.4			67.4
Less amounts representing interest	(3,374.3		)	(37.2		)
Total lease liability	6,923.1			30.2
Less current portion of lease liability	(475.1		)	(7.1		)
Non-current lease liability	$	6,448.0		$	23.1

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Future minimum rental payments under non-cancellable operating leases as of December 31, 2018 is as follows:



Year Ended December 31,	Amount (1)
2019	$	926.0
2020	904.2
2021	879.8
2022	834.2
2023	792.6
Thereafter	6,173.1
Total	$	10,509.9

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Future minimum rental payments under capital leases in effect as of December 31, 2018 were as follows:



Year Ended December 31,	Amount (1)
2019	$	40.7
2020	32.7
2021	27.8
2022	23.7
2023	19.2
Thereafter	117.5
Total	261.6
Less amounts representing interest	(82.1		)
Present value of capital lease obligations	$	179.5

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Included in the future minimum rental payments under capital leases and amounts representing interest as of December 31, 2018 were $220.3 million and $69.3 million, respectively, related to perpetual land easements, which are not accounted for as finance leases under the new lease accounting standard.

LEASES



Fiscal Year	Amount (1)
Remainder of 2019	$	1,394.7
2020	5,645.9
2021	5,442.0
2022	4,846.6
2023	4,710.8
Thereafter	24,225.4
Total	$	46,265.4

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Future minimum rental receipts expected under non-cancellable operating lease agreements in effect at December 31, 2018 were as follows:



Year Ended December 31,	Amount (1)
2019	$	5,251.2
2020	5,062.2
2021	4,676.1
2022	3,754.6
2023	3,457.3
Thereafter	12,641.1
Total	$	34,842.5

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Information about other lease-related balances as of September 30, 2019 is as follows:



Operating leases:
Right-of-use asset	$	7,214.7

Current portion of lease liability	$	475.1
Lease liability	6,448.0
Total operating lease liability	$	6,923.1

Finance leases:
Current portion of lease liability	$	7.1
Lease liability	23.1
Total finance lease liability	$	30.2

The weighted-average remaining lease terms and incremental borrowing rates as of September 30, 2019 are as follows:



Operating leases:
Weighted-average remaining lease term (years)	13.3
Weighted-average incremental borrowing rate	6.3	%

Finance leases:
Weighted-average remaining lease term (years)	15.0
Weighted-average incremental borrowing rate	6.2	%

The following table sets forth the components of lease cost for the three and nine months ended September 30, 2019:



	Three Months Ended September 30, 2019		Nine Months Ended September 30, 2019
Operating lease cost	$	249.5	$	760.3
Variable lease costs not included in lease liability (1)	67.7		190.8

_______________


(1)	Includes property tax paid on behalf of the landlord.

Supplemental cash flow information for the nine months ended September 30, 2019 is as follows:



Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	(701.9	)
Operating cash flows from finance leases	$	(1.1	)
Financing cash flows from finance leases	$	(16.4	)

Non-cash items:
New operating leases	$	224.8
Operating lease modifications and reassessments	$	338.9

As of September 30, 2019, the Company does not have material operating or financing leases that have not yet commenced.

Maturities of operating and finance lease liabilities as of September 30, 2019 were as follows:



Fiscal Year	Operating Lease (1)			Finance Lease (1)
Remainder of 2019	$	217.4		$	2.8
2020	876.0			7.6
2021	860.4			4.9
2022	822.4			4.0
2023	785.4			2.6
Thereafter	6,735.8			45.5
Total lease payments	10,297.4			67.4
Less amounts representing interest	(3,374.3		)	(37.2		)
Total lease liability	6,923.1			30.2
Less current portion of lease liability	(475.1		)	(7.1		)
Non-current lease liability	$	6,448.0		$	23.1

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Future minimum rental payments under non-cancellable operating leases as of December 31, 2018 is as follows:



Year Ended December 31,	Amount (1)
2019	$	926.0
2020	904.2
2021	879.8
2022	834.2
2023	792.6
Thereafter	6,173.1
Total	$	10,509.9

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Future minimum rental payments under capital leases in effect as of December 31, 2018 were as follows:



Year Ended December 31,	Amount (1)
2019	$	40.7
2020	32.7
2021	27.8
2022	23.7
2023	19.2
Thereafter	117.5
Total	261.6
Less amounts representing interest	(82.1		)
Present value of capital lease obligations	$	179.5

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

LEASES



Fiscal Year	Amount (1)
Remainder of 2019	$	1,394.7
2020	5,645.9
2021	5,442.0
2022	4,846.6
2023	4,710.8
Thereafter	24,225.4
Total	$	46,265.4

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Future minimum rental receipts expected under non-cancellable operating lease agreements in effect at December 31, 2018 were as follows:



Year Ended December 31,	Amount (1)
2019	$	5,251.2
2020	5,062.2
2021	4,676.1
2022	3,754.6
2023	3,457.3
Thereafter	12,641.1
Total	$	34,842.5

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Information about other lease-related balances as of September 30, 2019 is as follows:



Operating leases:
Right-of-use asset	$	7,214.7

Current portion of lease liability	$	475.1
Lease liability	6,448.0
Total operating lease liability	$	6,923.1

Finance leases:
Current portion of lease liability	$	7.1
Lease liability	23.1
Total finance lease liability	$	30.2

The weighted-average remaining lease terms and incremental borrowing rates as of September 30, 2019 are as follows:



Operating leases:
Weighted-average remaining lease term (years)	13.3
Weighted-average incremental borrowing rate	6.3	%

Finance leases:
Weighted-average remaining lease term (years)	15.0
Weighted-average incremental borrowing rate	6.2	%

The following table sets forth the components of lease cost for the three and nine months ended September 30, 2019:



	Three Months Ended September 30, 2019		Nine Months Ended September 30, 2019
Operating lease cost	$	249.5	$	760.3
Variable lease costs not included in lease liability (1)	67.7		190.8

_______________


(1)	Includes property tax paid on behalf of the landlord.

Supplemental cash flow information for the nine months ended September 30, 2019 is as follows:



Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	(701.9	)
Operating cash flows from finance leases	$	(1.1	)
Financing cash flows from finance leases	$	(16.4	)

Non-cash items:
New operating leases	$	224.8
Operating lease modifications and reassessments	$	338.9

As of September 30, 2019, the Company does not have material operating or financing leases that have not yet commenced.

Maturities of operating and finance lease liabilities as of September 30, 2019 were as follows:



Fiscal Year	Operating Lease (1)			Finance Lease (1)
Remainder of 2019	$	217.4		$	2.8
2020	876.0			7.6
2021	860.4			4.9
2022	822.4			4.0
2023	785.4			2.6
Thereafter	6,735.8			45.5
Total lease payments	10,297.4			67.4
Less amounts representing interest	(3,374.3		)	(37.2		)
Total lease liability	6,923.1			30.2
Less current portion of lease liability	(475.1		)	(7.1		)
Non-current lease liability	$	6,448.0		$	23.1

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Future minimum rental payments under non-cancellable operating leases as of December 31, 2018 is as follows:



Year Ended December 31,	Amount (1)
2019	$	926.0
2020	904.2
2021	879.8
2022	834.2
2023	792.6
Thereafter	6,173.1
Total	$	10,509.9

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Future minimum rental payments under capital leases in effect as of December 31, 2018 were as follows:



Year Ended December 31,	Amount (1)
2019	$	40.7
2020	32.7
2021	27.8
2022	23.7
2023	19.2
Thereafter	117.5
Total	261.6
Less amounts representing interest	(82.1		)
Present value of capital lease obligations	$	179.5

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

GOODWILL AND OTHER INTANGIBLE ASSETS

9 Months Ended

Sep. 30, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL AND OTHER INTANGIBLE ASSETS

The changes in the carrying value of goodwill for each of the Company’s business segments were as follows:



	Property											Services		Total
	U.S.		Asia			EMEA			Latin America			Services		Total
Balance as of January 1, 2019	$	3,382.5	$	1,045.5		$	381.3		$	690.6		$	2.0	$	5,501.9
Additions and adjustments (1)	33.5		—			—			—			—		33.5
Effect of foreign currency translation	—		(16.3		)	(16.8		)	(20.9		)	—		(54.0		)
Balance as of September 30, 2019	$	3,416.0	$	1,029.2		$	364.5		$	669.7		$	2.0	$	5,481.4

_______________


(1)	Additions consist of $34.3 million resulting from 2019 acquisitions offset by $0.8 million from revisions to prior-year acquisitions due to measurement period adjustments.

The Company’s other intangible assets subject to amortization consisted of the following:



		As of September 30, 2019							As of December 31, 2018
	Estimated Useful Lives (years)	Gross Carrying Value		Accumulated Amortization			Net Book Value		Gross Carrying Value		Accumulated Amortization			Net Book Value
Acquired network location intangibles (1)	Up to 20	$	4,832.7	$	(1,863.2	)	$	2,969.5	$	4,780.3	$	(1,704.9	)	$	3,075.4
Acquired tenant-related intangibles	15-20	11,359.2		(3,517.3		)	7,841.9		11,156.5		(3,147.2		)	8,009.3
Acquired licenses and other intangibles	3-20	103.9		(19.5		)	84.4		104.1		(14.5		)	89.6
Total other intangible assets		$	16,295.8	$	(5,400.0	)	$	10,895.8	$	16,040.9	$	(4,866.6	)	$	11,174.3

_______________


(1)	Acquired network location intangibles are amortized over the shorter of the term of the corresponding ground lease, taking into consideration lease renewal options and residual value, or up to 20 years, as the Company considers these intangibles to be directly related to the tower assets.

The acquired network location intangibles represent the value to the Company of the incremental revenue growth that could potentially be obtained from leasing the excess capacity on acquired communications sites. The acquired tenant-related intangibles typically represent the value to the Company of tenant contracts and relationships in place at the time of an acquisition or similar transaction, including assumptions regarding estimated renewals.

The Company amortizes its acquired network location intangibles and tenant-related intangibles on a straight-line basis over their estimated useful lives. As of September 30, 2019, the remaining weighted average amortization period of the Company’s intangible assets was 14 years. Amortization of intangible assets for the three and nine months ended September 30, 2019 was $197.9 million and $590.2 million, respectively, and amortization of intangible assets for the three and nine months ended September 30, 2018 was $207.4 million and $615.0 million, respectively. Based on current exchange rates, the Company expects to record amortization expense as follows over the remaining current year and the five subsequent years:



Fiscal Year	Amount
Remainder of 2019	$	199.0
2020	777.8
2021	761.7
2022	757.7
2023	753.8
2024	750.8

LONG-TERM OBLIGATIONS

9 Months Ended

Sep. 30, 2019

Debt Disclosure [Abstract]

LONG-TERM OBLIGATIONS

Outstanding amounts under the Company’s long-term obligations, reflecting discounts, premiums, debt issuance costs and fair value adjustments due to interest rate swaps consisted of the following:



	As of
	September 30, 2019			December 31, 2018			Maturity Date
2018 Term Loan (1) (2)	$	—		$	1,499.8		March 29, 2019
2019 Term Loan (1)	1,299.8			—			February 13, 2020
2013 Credit Facility (1)	1,122.0			1,875.0			June 28, 2022
2013 Term Loan (1)	995.5			994.8			January 31, 2024
2014 Credit Facility (1)	—			—			January 31, 2024
3.40% senior notes (3)	—			1,000.0			February 15, 2019
2.800% senior notes	749.0			747.8			June 1, 2020
5.050% senior notes (4)	—			698.7			September 1, 2020
3.300% senior notes	748.2			747.2			February 15, 2021
3.450% senior notes	647.3			646.3			September 15, 2021
5.900% senior notes	498.8			498.4			November 1, 2021
2.250% senior notes	592.0			572.7			January 15, 2022
4.70% senior notes	698.0			697.4			March 15, 2022
3.50% senior notes	993.8			992.6			January 31, 2023
3.000% senior notes	708.0			687.5			June 15, 2023
5.00% senior notes	1,001.8			1,002.1			February 15, 2024
3.375% senior notes	644.1			—			May 15, 2024
2.950% senior notes	640.9			—			January 15, 2025
1.375% senior notes	537.1			564.0			April 4, 2025
4.000% senior notes	742.9			742.1			June 1, 2025
4.400% senior notes	496.5			496.1			February 15, 2026
1.950% senior notes	538.6			566.0			May 22, 2026
3.375% senior notes	987.5			986.3			October 15, 2026
3.125% senior notes	397.6			397.3			January 15, 2027
3.55% senior notes	744.0			743.5			July 15, 2027
3.600% senior notes	692.4			691.9			January 15, 2028
3.950% senior notes	589.4			—			March 15, 2029
3.800% senior notes	1,631.3			—			August 15, 2029
Total American Tower Corporation debt	18,696.5			17,847.5

Series 2013-2A securities (5)	1,294.6			1,293.4			March 15, 2023
Series 2018-1A securities (5)	493.7			493.5			March 15, 2028
Series 2015-1 notes (6)	349.4			348.8			June 15, 2020
Series 2015-2 notes (7)	521.3			520.8			June 16, 2025
India indebtedness (8)	—			240.1			Various
India preference shares (9)	—			23.9			March 2, 2020
Shareholder loan (10)	—			59.9			December 31, 2019
Other subsidiary debt (11)	97.9			152.5			Various
Total American Tower subsidiary debt	2,756.9			3,132.9
Finance and capital lease obligations	30.2			179.5
Total	21,483.6			21,159.9
Less current portion of long-term obligations	(2,443.6		)	(2,754.8		)
Long-term obligations	$	19,040.0		$	18,405.1

_______________


(1)	Accrues interest at a variable rate.


(2)	Repaid in full on February 14, 2019 using proceeds from the 2019 Term Loan (as defined below) and cash on hand.


(3)	Repaid in full on the maturity date in February 2019 with borrowings from the 2013 Credit Facility and the 2014 Credit Facility (each as defined below).


(4)	Repaid in full on April 22, 2019 with borrowings from the 2014 Credit Facility and cash on hand.


(5)	Maturity date reflects the anticipated repayment date; final legal maturity is March 15, 2048.


(6)	Maturity date reflects the anticipated repayment date; final legal maturity is June 15, 2045.


(7)	Maturity date reflects the anticipated repayment date; final legal maturity is June 15, 2050.

(8)

Denominated in Indian Rupees (“INR”). Included India working capital facilities, remaining debt assumed by the Company in connection with the Viom Acquisition (as defined in note 12) and debt that had been entered into by ATC TIPL. During the three months ended March 31, 2019, the Company repaid all remaining debt assumed in connection with the Viom Acquisition and debt entered into by ATC TIPL.


(9)	Mandatorily redeemable preference shares (the “Preference Shares”) denominated in INR and classified as debt. The Preference Shares were redeemed on March 2, 2019.

(10)

Reflects balance owed to the Company’s joint venture partner in Ghana. The Ghana loan is denominated in Ghanaian Cedi (“GHS”). On June 14, 2019, the Company purchased the remaining 294.4 million GHS ($56.8 million) of principal outstanding under the Ghana loan, plus unpaid interest. Amounts under the loan are now owed to one of the Company’s subsidiaries and, as a result, are eliminated in consolidation as of the purchase date.

(11)

Includes the South African credit facility, which is denominated in South African Rand and amortizes through December 17, 2020, the Colombian credit facility, which is denominated in Colombian Pesos and amortizes through April 24, 2021, the Brazil credit facility, which is denominated in Brazilian Reais and amortizes through January 15, 2022, the Kenya debt, which is denominated in U.S. Dollars (“USD”) and is payable either (i) in future installments subject to the satisfaction of specified conditions or (ii) three years from the note origination date, and U.S. subsidiary debt related to a seller-financed acquisition.

Current portion of long-term obligations—The Company’s current portion of long-term obligations primarily includes (i) $1.3 billion under its unsecured term loan entered into on February 14, 2019 (the “2019 Term Loan”), (ii) $750.0 million aggregate principal amount of 2.800% senior unsecured notes due 2020 and (iii) $350.0 million aggregate principal amount of the American Tower Secured Revenue Notes, Series 2015-1, Class A, issued by GTP Acquisition Partners I, LLC in a private securitization transaction in May 2015, with anticipated repayment date in 2020.

Securitized Debt—Cash flows generated by the sites that secure the securitized debt of the Company are only available for payment of such debt and are not available to pay the Company’s other obligations or the claims of its creditors. However, subject to certain restrictions, the Company holds the right to receive the excess cash flows not needed to pay the securitized debt and other obligations arising out of the securitizations. The securitized debt is the obligation of the issuers thereof or borrowers thereunder, as applicable, and their subsidiaries, and not of the Company or its other subsidiaries.

Repayments of Senior Notes

Repayment of 3.40% Senior Notes—On the February 15, 2019 maturity date, the Company repaid $1.0 billion aggregate principal amount of 3.40% senior unsecured notes due 2019 (the “3.40% Notes”). The 3.40% Notes were repaid with borrowings from the Company’s multicurrency senior unsecured revolving credit facility entered into in June 2013, as amended (the “2013 Credit Facility”) and the Company’s senior unsecured revolving credit facility entered into in January 2012 and amended and restated in September 2014, as further amended (the “2014 Credit Facility”). Upon completion of the repayment, none of the 3.40% Notes remained outstanding.

Repayment of 5.050% Senior Notes—On April 22, 2019, the Company redeemed all of the $700.0 million aggregate principal amount of 5.050% senior unsecured notes due 2020 (the “5.050% Notes”) at a price equal to 103.0050% of the principal amount, plus accrued and unpaid interest up to, but excluding April 22, 2019, for an aggregate redemption price of $726.0 million, including $5.0 million in accrued and unpaid interest. The Company recorded a loss on retirement of long-term obligations of $22.1 million, which includes prepayment consideration of $21.0 million and the associated unamortized discount and deferred financing costs. The redemption was funded with borrowings from the 2014 Credit Facility and cash on hand. Upon completion of the repayment, none of the 5.050% Notes remained outstanding.

Offerings of Senior Notes

3.375% Senior Notes and 3.950% Senior Notes Offering—On March 15, 2019, the Company completed a registered public offering of $650.0 million aggregate principal amount of 3.375% senior unsecured notes due 2024 (the “3.375% Notes”) and $600.0 million aggregate principal amount of 3.950% senior unsecured notes due 2029 (the “3.950% Notes”). The net proceeds from this offering were approximately $1,231.0 million, after deducting

commissions and estimated expenses. The Company used the net proceeds to repay existing indebtedness under the 2013 Credit Facility and the 2014 Credit Facility.

The 3.375% Notes will mature on May 15, 2024 and bear interest at a rate of 3.375% per annum. The 3.950% Notes will mature on March 15, 2029 and bear interest at a rate of 3.950% per annum. Accrued and unpaid interest on the 3.375% Notes will be payable in U.S. Dollars semi-annually in arrears on May 15 and November 15 of each year, beginning on November 15, 2019. Accrued and unpaid interest on the 3.950% Notes will be payable in U.S. Dollars semi-annually in arrears on March 15 and September 15 of each year, beginning on September 15, 2019. Interest on the 3.375% Notes and the 3.950% Notes will accrue from March 15, 2019 and will be computed on the basis of a 360-day year comprised of twelve 30-day months.

2.950% Senior Notes and 3.800% Senior Notes Offering—On June 13, 2019, the Company completed a registered public offering of $650.0 million aggregate principal amount of 2.950% senior unsecured notes due 2025 (the “2.950% Notes”) and $1.65 billion aggregate principal amount of 3.800% senior unsecured notes due 2029 (the “3.800% Notes” and, collectively with the 3.375% Notes, the 3.950% Notes and the 2.950% Notes, the “Notes”). The net proceeds from this offering were approximately $2,269.0 million, after deducting commissions and estimated expenses. The Company used the net proceeds to repay existing indebtedness under the 2013 Credit Facility and the 2014 Credit Facility.

The 2.950% Notes will mature on January 15, 2025 and bear interest at a rate of 2.950% per annum. The 3.800% Notes will mature on August 15, 2029 and bear interest at a rate of 3.800% per annum. Accrued and unpaid interest on the 2.950% Notes will be payable in U.S. Dollars semi-annually in arrears on January 15 and July 15 of each year, beginning on January 15, 2020. Accrued and unpaid interest on the 3.800% Notes will be payable in U.S. Dollars semi-annually in arrears on February 15 and August 15 of each year, beginning on February 15, 2020. Interest on the 2.950% Notes and the 3.800% Notes will accrue from June 13, 2019 and will be computed on the basis of a 360-day year comprised of twelve 30-day months.

The Company may redeem the Notes at any time, in whole or in part, at a redemption price equal to 100% of the principal amount of the Notes plus a make-whole premium, together with accrued interest to the redemption date. If the Company redeems the 3.375% Notes on or after April 15, 2024, the 2.950% Notes on or after December 15, 2024, the 3.950% Notes on or after December 15, 2028 or the 3.800% Notes on or after May 15, 2029, it will not be required to pay a make-whole premium. In addition, if the Company undergoes a change of control and corresponding ratings decline, each as defined in the applicable supplemental indenture, it may be required to repurchase all of the Notes at a purchase price equal to 101% of the principal amount of such Notes, plus accrued and unpaid interest (including additional interest, if any), up to but not including the repurchase date. The Notes rank equally with all of the Company’s other senior unsecured debt and are structurally subordinated to all existing and future indebtedness and other obligations of its subsidiaries.

The supplemental indentures contain certain covenants that restrict the Company’s ability to merge, consolidate or sell assets and its (together with its subsidiaries’) ability to incur liens. These covenants are subject to a number of exceptions, including that the Company and its subsidiaries may incur certain liens on assets, mortgages or other liens securing indebtedness if the aggregate amount of indebtedness secured by such liens does not exceed 3.5x Adjusted EBITDA, as defined in the applicable supplemental indenture.

Bank Facilities

2013 Credit Facility—During the nine months ended September 30, 2019, the Company borrowed an aggregate of $1.7 billion and repaid an aggregate of $2.5 billion of revolving indebtedness under the 2013 Credit Facility. The Company used the borrowings to fund acquisitions, to purchase redeemable noncontrolling interests, to repay existing indebtedness and for general corporate purposes.

2014 Credit Facility—During the nine months ended September 30, 2019, the Company borrowed an aggregate of $1.6 billion and repaid an aggregate of $1.6 billion of revolving indebtedness under the 2014 Credit Facility. The Company used the borrowings to repay existing indebtedness and for general corporate purposes.

2019 Term Loan—During the nine months ended September 30, 2019, the Company entered into the 2019 Term Loan, the net proceeds of which were used, together with cash on hand, to repay all outstanding indebtedness under its $1.5 billion unsecured term loan entered into on March 29, 2018.

The 2019 Term Loan matures on February 13, 2020. Any outstanding principal and accrued but unpaid interest will be due and payable in full at maturity. The 2019 Term Loan may be paid prior to maturity in whole or in part at the Company’s option without penalty or premium.

The 2019 Term Loan agreement contains certain reporting, information, financial and operating covenants and other restrictions (including limitations on additional debt, guaranties, sales of assets and liens) with which the Company must comply. Failure to comply with the financial and operating covenants of the loan agreement may constitute a default, which could result in, among other things, the amounts outstanding, including all accrued interest and unpaid fees, becoming immediately due and payable.

As of September 30, 2019, the key terms under the 2013 Credit Facility, the 2014 Credit Facility, the Company’s unsecured term loan entered into in October 2013, as amended (the “2013 Term Loan”), and the 2019 Term Loan were as follows:



	Outstanding Principal Balance (in millions)		Undrawn letters of credit (in millions)		Maturity Date		Current margin over LIBOR (1)		Current commitment fee (2)
2013 Credit Facility	$	1,122.0	$	3.8	June 28, 2022	(3)	1.125	%	0.125	%
2014 Credit Facility	$	—	$	6.2	January 31, 2024	(3)	1.125	%	0.125	%
2013 Term Loan	$	1,000.0	N/A		January 31, 2024		1.125	%	N/A
2019 Term Loan	$	1,300.0	N/A		February 13, 2020		0.800	%	N/A

_______________

(1) LIBOR means the London Interbank Offered Rate.

(2) Fee on undrawn portion of each credit facility.

(3) Subject to two optional renewal periods.

FAIR VALUE MEASUREMENTS

9 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

The Company determines the fair value of its financial instruments based on the fair value hierarchy, which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. Below are the three levels of inputs that may be used to measure fair value:



	Level 1	Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

	Level 2	Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

	Level 3	Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

Items Measured at Fair Value on a Recurring Basis—The fair values of the Company’s financial assets and liabilities that are required to be measured on a recurring basis at fair value were as follows:



	September 30, 2019						December 31, 2018
	Fair Value Measurements Using						Fair Value Measurements Using
	Level 1		Level 2		Level 3		Level 1			Level 2		Level 3
Assets:
Interest rate swap agreements	—		$	12.7	—		—			—		—
Embedded derivative in lease agreement	—		—		$	10.9	—			—		$	11.5
Liabilities:
Interest rate swap agreements	—		$	7.3	—		—			$	33.8	—
Acquisition-related contingent consideration	—		—		$	0.8	—			—		$	0.9
Fair value of debt related to interest rate swap agreements (1)	$	7.0	—		—		$	(31.3	)	—		—
Redeemable noncontrolling interests	—		—		$	574.8	—			—		$	1,004.8

_______________


(1)	Included in the carrying values of the corresponding debt obligations.

During the nine months ended September 30, 2019, the Company made no changes to the methods described in note 11 to its consolidated financial statements included in the 2018 Form 10-K that it used to measure the fair value of its interest rate swap agreements, the embedded derivative in one of its lease agreements, acquisition-related contingent consideration and redeemable noncontrolling interests. The changes in fair value for the embedded derivative in one of its lease agreements and acquisition-related contingent consideration during the nine months ended September 30, 2019 and 2018 were not material to the consolidated financial statements. The changes in the carrying amount of the redeemable noncontrolling interests are described in note 12. As of September 30, 2019, the Company estimated the value of all potential acquisition-related contingent consideration payments to be between zero and $0.8 million.

Items Measured at Fair Value on a Nonrecurring Basis

Assets Held and Used—The Company’s long-lived assets are recorded at amortized cost and, if impaired, are adjusted to fair value using Level 3 inputs. The Company recorded $14.0 million and $45.1 million of impairments during the three and nine months ended September 30, 2019, respectively, and $1.8 million and $182.4 million of impairments during the three and nine months ended September 30, 2018, respectively. There were no other items measured at fair value on a nonrecurring basis during the nine months ended September 30, 2019 or 2018.

Fair Value of Financial Instruments—The Company’s financial instruments for which the carrying value reasonably approximates fair value at September 30, 2019 and December 31, 2018 include cash and cash equivalents, restricted cash, accounts receivable and accounts payable. The Company’s estimates of fair value of its long-term obligations, including the current portion, are based primarily upon reported market values. For long-term debt not actively traded, fair value is estimated using either indicative price quotes or a discounted cash flow analysis using rates for debt with similar terms and maturities. As of September 30, 2019 and December 31, 2018, the carrying value of long-term obligations, including the current portion, was $21.5 billion and $21.2 billion, respectively. As of September 30, 2019, the fair value of long-term obligations, including the current portion, was $22.4 billion, of which $16.1 billion was measured using Level 1 inputs and $6.3 billion was measured using Level 2 inputs. As of December 31, 2018, the fair value of long-term obligations, including the current portion, was $21.1 billion, of which $13.4 billion was measured using Level 1 inputs and $7.7 billion was measured using Level 2 inputs.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

INCOME TAXES

9 Months Ended

Sep. 30, 2019

Income Tax Disclosure [Abstract]

INCOME TAXES

The Company provides for income taxes at the end of each interim period based on the estimated effective tax rate (“ETR”) for the full fiscal year. Cumulative adjustments to the Company’s estimate are recorded in the interim period in which a change in the estimated annual ETR is determined. Under the provisions of the Internal Revenue Code of 1986, as amended, the Company may deduct amounts distributed to stockholders against the income generated by its real estate investment trust (“REIT”) operations. The Company continues to be subject to income taxes on the income of its domestic taxable REIT subsidiaries and income taxes in foreign jurisdictions where it conducts operations. In addition, the Company is able to offset certain income by utilizing its net operating losses, subject to specified limitations.

The Company provides valuation allowances if, based on the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. Management assesses the available evidence to estimate if sufficient future taxable income will be generated to use the existing deferred tax assets.

The increase in the income tax provision during the three months ended September 30, 2019 was primarily attributable to an increase in foreign earnings subject to taxation in the current period. The change in the income tax provision (benefit) for the nine months ended September 30, 2019 was primarily attributable to an increase in foreign earnings subject to taxation in the current period, as well as the nonrecurrence of certain events during the nine months ended September 30, 2018, including a one-time benefit for merger-related activity in the Company’s Asia property segment and the tax effect of certain impairment charges.

As of September 30, 2019 and December 31, 2018, the total unrecognized tax benefits that would impact the ETR, if recognized, were approximately $93.3 million and $93.7 million, respectively. The amount of unrecognized tax benefits during the three and nine months ended September 30, 2019 includes additions to the Company’s existing tax positions of $1.4 million and $4.4 million, respectively, which were reduced by foreign currency exchange rate fluctuations of $3.7 million and $2.7 million, respectively. Unrecognized tax benefits are expected to change over the next 12 months if certain tax matters ultimately settle with the applicable taxing jurisdiction during this time frame, as described in note 12 to the Company’s consolidated financial statements included in the 2018 Form 10-K. The impact of the amount of these changes to previously recorded uncertain tax positions could range from zero to $27.5 million.

The Company recorded the following penalties and income tax-related interest expense during the three and nine months ended September 30, 2019 and 2018:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Penalties and income tax-related interest expense	$	2.1	$	1.0	$	4.3	$	2.7

As of September 30, 2019 and December 31, 2018, the total amount of accrued income tax related interest and penalties included in the consolidated balance sheets were $22.7 million and $19.1 million, respectively.

STOCK-BASED COMPENSATION

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

STOCK-BASED COMPENSATION

Summary of Stock-Based Compensation Plans—The Company maintains equity incentive plans that provide for the grant of stock-based awards to its directors, officers and employees. The 2007 Equity Incentive Plan, as amended (the “2007 Plan”), provides for the grant of non-qualified and incentive stock options, as well as restricted stock units, restricted stock and other stock-based awards. Exercise prices for non-qualified and incentive stock options are not less than the fair value of the underlying common stock on the date of grant. Equity awards typically vest ratably, generally over four years for time-based restricted stock units (“RSUs”) and stock options and three years for performance-based restricted stock units (“PSUs”). Stock options generally expire ten years from the date of grant. As of September 30, 2019, the Company had the ability to grant stock-based awards with respect to an aggregate of 7.0 million shares of common stock under the 2007 Plan. In addition, the Company maintains an employee stock purchase plan (the “ESPP”) pursuant to which eligible employees may purchase shares of the Company’s common stock on the last day of each bi-annual offering period at a 15% discount from the lower of the closing market value on the first or last day of such offering period. The offering periods run from June 1 through November 30 and from December 1 through May 31 of each year.

During the three and nine months ended September 30, 2019 and 2018, the Company recorded and capitalized the following stock-based compensation expense:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Stock-based compensation expense Property	$	0.4	$	0.8	$	1.4	$	2.0
Stock-based compensation expense Services	0.2		0.2		0.7		0.7
Stock-based compensation expense SG&A	22.9		42.8		85.8		108.6
Total stock-based compensation expense	$	23.5	$	43.8	$	87.9	$	111.3

Stock-based compensation expense capitalized as property and equipment	$	0.3	$	0.6	$	1.2	$	1.6

Stock Options—As of September 30, 2019, total unrecognized compensation expense related to unvested stock options was $1.4 million, which is expected to be recognized over a weighted average period of less than one year.

The Company’s option activity for the nine months ended September 30, 2019 was as follows (shares disclosed in full amounts):



	Number of Options
Outstanding as of January 1, 2019	4,257,470
Granted	—
Exercised	(1,080,169	)
Forfeited	(7,211	)
Expired	—
Outstanding as of September 30, 2019	3,170,090

Restricted Stock Units—As of September 30, 2019, total unrecognized compensation expense related to unvested RSUs granted under the 2007 Plan was $137.8 million and is expected to be recognized over a weighted average period of approximately two years. Vesting of RSUs is subject generally to the employee’s continued employment or death, disability or qualified retirement (each as defined in the applicable RSU award agreement).

Performance-Based Restricted Stock Units—During the nine months ended September 30, 2019, 2018 and 2017, the Company’s Compensation Committee granted an aggregate of 114,823 PSUs (the “2019 PSUs”), 131,311 PSUs (the “2018 PSUs”) and 154,520 PSUs (the “2017 PSUs”), respectively, to its executive officers and established the performance metrics for these awards. Threshold, target and maximum parameters were established for the metrics for a three-year performance period with respect to each of the 2019 PSUs, the 2018 PSUs and the 2017 PSUs and will be used to calculate the number of shares that will be issuable when each award vests, which may range from zero to 200% of the target amounts. At the end of each three-year performance period, the number of shares that vest will depend on the degree of achievement against the pre-established performance goals. PSUs will be paid out in common stock at the end of each performance period, subject generally to the executive’s continued employment or death, disability or qualified retirement (each as defined in the applicable PSU award agreement). PSUs will accrue dividend equivalents prior to vesting, which will be paid out only in respect of shares that actually vest.

Restricted Stock Units and Performance-Based Restricted Stock Units—The Company’s RSU and PSU activity for the nine months ended September 30, 2019 was as follows (shares disclosed in full amounts):



	RSUs		PSUs
Outstanding as of January 1, 2019 (1)	1,649,973		624,511
Granted (2)	542,744		114,823
Vested and Released (3)	(661,333	)	(338,680	)
Forfeited	(60,856	)	—
Outstanding as of September 30, 2019	1,470,528		400,654
Vested and deferred as of September 30, 2019 (4)	19,810		—

_______________

(1)

PSUs consist of the target number of shares issuable at the end of the three-year performance period for the 2018 PSUs and 2017 PSUs, or 131,311 and 154,520 shares, respectively, and the shares issuable at the end of the three-year performance period for the PSUs granted in 2016 (“2016 PSUs”) based on achievement against the performance metrics for the three-year performance period, or 338,680 shares.


(2)	PSUs consist of the target number of shares issuable at the end of the three-year performance period for the 2019 PSUs, or 114,823 shares.


(3)	This includes 32,596 and 46,500 of previously vested and deferred RSUs and PSUs, respectively. PSUs consist of shares vested pursuant to the 2016 PSUs. There are no additional shares to be earned related to the 2016 PSUs.


(4)	Vested and deferred RSUs are related to deferred compensation for certain former employees.

During the three and nine months ended September 30, 2019, the Company recorded $4.6 million and $18.1 million, respectively, in stock-based compensation expense for equity awards in which the performance goals have been established and were probable of being achieved. The remaining unrecognized compensation expense related to these awards at September 30, 2019 was $15.0 million based on the Company’s current assessment of the probability of achieving the performance goals. The weighted average period over which the cost will be recognized is approximately two years.

REDEEMABLE NONCONTROLLING INTERESTS

9 Months Ended

Sep. 30, 2019

Noncontrolling Interest [Abstract]

REDEEMABLE NONCONTROLLING INTERESTS

Redeemable Noncontrolling Interests—On April 21, 2016, the Company, through its wholly owned subsidiary, ATC Asia Pacific Pte. Ltd., acquired a 51% controlling ownership interest in ATC TIPL (formerly Viom), a telecommunications infrastructure company that owns and operates wireless communications towers and indoor DAS networks in India (the “Viom Acquisition”), which was subsequently merged with the Company’s existing India property operations.

In connection with the Viom Acquisition, the Company, through one of its subsidiaries, entered into a shareholders agreement (the “Shareholders Agreement”) with Viom and the following remaining Viom shareholders: Tata Sons Limited (“Tata Sons”), Tata Teleservices Limited (“Tata Teleservices”), IDFC Private Equity Fund III (“IDFC”), Macquarie SBI Infrastructure Investments Pte Limited and SBI Macquarie Infrastructure Trust (collectively, the “Remaining Shareholders”).

The Shareholders Agreement also provides the Remaining Shareholders with put options, which allow them to sell outstanding shares of ATC TIPL to the Company, and the Company with call options, which allow it to buy the noncontrolling shares of ATC TIPL. The put options, which are not under the Company’s control, cannot be separated from the noncontrolling interests. As a result, the combination of the noncontrolling interests and the redemption feature requires classification as redeemable noncontrolling interests in the consolidated balance sheet, separate from equity.

The noncontrolling interests become redeemable after the passage of time, and therefore, the Company records the carrying amount of the noncontrolling interests outside of permanent equity at the greater of (i) the initial carrying amount, increased or decreased for the noncontrolling interests’ share of net income or loss and foreign currency translation adjustments, or (ii) the estimated redemption value. If required, the Company will adjust the redeemable noncontrolling interests to the estimated redemption value on each balance sheet date with changes in the estimated redemption value recognized as an adjustment to Net income attributable to noncontrolling interests. The Company adjusts the estimated redemption value of the noncontrolling interests based on the operating results of ATC TIPL and previously recorded adjustments to the estimated redemption value. During the nine months ended September 30, 2019, the Company reduced the estimated redemption value of the noncontrolling interests by $2.2 million. During the nine months ended September 30, 2018, the Company increased the estimated redemption value of the noncontrolling

interests by $28.6 million. The adjustment for the nine months ended September 30, 2018 was primarily due to the impact of impairment charges on net income and, as a result, on the carrying value of the noncontrolling interests.

The put options may be exercised, requiring the Company to purchase the Remaining Shareholders’ equity interests, on specified dates through March 31, 2021. The price of the put options will be based on the fair market value of the exercising Remaining Shareholders’ interest in the Company’s India operations at the time the option is exercised. Put options held by certain of the Remaining Shareholders are subject to a floor price of INR 216 per share.

During the nine months ended September 30, 2019, the Company redeemed 50% of Tata Teleservices and Tata Sons’ combined holdings of ATC TIPL and 100% of IDFC’s holdings of ATC TIPL, for total consideration of INR 29.4 billion ($425.7 million at the date of redemption). As a result of the redemption, the Company’s controlling interest in ATC TIPL increased from 63% to 79% and the noncontrolling interest decreased from 37% to 21%.

The changes in Redeemable noncontrolling interests for the nine months ended September 30, 2019 and 2018 were as follows:



	2019			2018
Balance as of January 1,	$	1,004.8		$	1,126.2
Net income (loss) attributable to noncontrolling interests	2.2			(42.4		)
Adjustment to noncontrolling interest redemption value	(2.2		)	28.6
Adjustment to noncontrolling interest due to merger	—			(28.1		)
Purchase of redeemable noncontrolling interest	(425.7		)	—
Foreign currency translation adjustment attributable to noncontrolling interests	(4.3		)	(129.5		)
Balance as of September 30,	$	574.8		$	954.8

In April 2019, Tata Teleservices and Tata Sons delivered notice of exercise of their put options with respect to 100% of their remaining holdings in ATC TIPL. The Company expects to complete the redemption of the put shares, subject to regulatory approval, for total consideration of INR 24.8 billion (approximately $350.1 million at the September 30, 2019 exchange rate) in the fourth quarter of 2019. After the completion of the redemption, the Company will hold an approximately 92% ownership interest in ATC TIPL.

EQUITY

9 Months Ended

Sep. 30, 2019

Equity [Abstract]

EQUITY

Sales of Equity Securities—The Company receives proceeds from the sale of its equity securities pursuant to the ESPP and upon exercise of stock options granted under the 2007 Plan. During the nine months ended September 30, 2019, the Company received an aggregate of $92.7 million in proceeds upon exercises of stock options and sales pursuant to the ESPP.

Stock Repurchase Programs—In March 2011, the Board of Directors approved a stock repurchase program, pursuant to which the Company is authorized to repurchase up to $1.5 billion of its common stock (the “2011 Buyback”). In December 2017, the Board of Directors approved an additional stock repurchase program, pursuant to which the Company is authorized to repurchase up to $2.0 billion of its common stock (the “2017 Buyback” and, together with the 2011 Buyback, the “Buyback Programs”).

During the nine months ended September 30, 2019, there were no repurchases under either of the Buyback Programs. As of September 30, 2019, the Company has repurchased a total of 14,003,543 shares of its common stock under the 2011 Buyback for an aggregate of $1.4 billion, including commissions and fees. The Company has not made any repurchases under the 2017 Buyback.

Under the Buyback Programs, the Company is authorized to purchase shares from time to time through open market purchases, in privately negotiated transactions not to exceed market prices, and (with respect to such open market purchases) pursuant to plans adopted in accordance with Rule 10b5-1 under the Securities Exchange Act of 1934, as

amended, in accordance with securities laws and other legal requirements and subject to market conditions and other factors.

The Company expects to fund any further purchases of its common stock through a combination of cash on hand, cash generated by operations and borrowings under its credit facilities. Purchases under the Buyback Programs are subject to, among other things, the Company having available cash to fund the purchases.

Distributions—During the nine months ended September 30, 2019, the Company declared or paid the following cash distributions (per share data reflects actual amounts):



Declaration Date	Payment Date	Record Date	Distribution per share		Aggregate Payment Amount (1)
Common Stock
September 13, 2019	October 17, 2019	September 27, 2019	$	0.95	$	420.7
May 22, 2019	July 12, 2019	June 19, 2019	$	0.92	$	407.0
March 7, 2019	April 26, 2019	April 11, 2019	$	0.90	$	397.8
December 5, 2018	January 14, 2019	December 27, 2018	$	0.84	$	370.5


(1)	Does not include amounts accrued for distributions payable related to unvested restricted stock units.

During the nine months ended September 30, 2018, the Company declared or paid the following cash distributions (per share data reflects actual amounts):



Declaration Date	Payment Date	Record Date	Distribution per share		Aggregate Payment Amount (1)
Common Stock
September 6, 2018	October 17, 2018	September 28, 2018	$	0.79	$	348.3
May 24, 2018	July 13, 2018	June 19, 2018	$	0.77	$	339.8
March 8, 2018	April 27, 2018	April 11, 2018	$	0.75	$	331.2
December 6, 2017	January 16, 2018	December 28, 2017	$	0.70	$	300.2

Series B Preferred Stock
January 22, 2018	February 15, 2018	February 1, 2018	$	13.75	$	18.9


(1)	Does not include amounts accrued for distributions payable related to unvested restricted stock units.

The Company accrues distributions on unvested restricted stock units, which are payable upon vesting. As of September 30, 2019, the amount accrued for distributions payable related to unvested restricted stock units was $12.3 million. During the nine months ended September 30, 2019 and 2018, the Company paid $6.9 million and $4.2 million of distributions upon the vesting of restricted stock units, respectively. To maintain its qualification for taxation as a REIT, the Company expects to continue paying distributions, the amount, timing and frequency of which will be determined, and subject to adjustment, by the Company’s Board of Directors.

COMMITMENTS AND CONTINGENCIES	9 Months Ended
COMMITMENTS AND CONTINGENCIES	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Litigation—The Company periodically becomes involved in various claims, lawsuits and proceedings that are incidental to its business. In the opinion of Company management, after consultation with counsel, there are no matters currently pending that would, in the event of an adverse outcome, materially impact the Company’s consolidated financial position, results of operations or liquidity. Verizon Transaction—In March 2015, the Company entered into an agreement with various operating entities of Verizon Communications Inc. (“Verizon”) that currently provides for the lease, sublease or management of approximately 11,250 wireless communications sites commencing March 27, 2015. The average term of the lease or sublease for all sites at the inception of the agreement was approximately 28 years, assuming renewals or extensions of the underlying ground leases for the sites. The Company has the option to purchase the leased sites in tranches, subject to the applicable lease, sublease or management rights upon its scheduled expiration. Each tower is assigned to an annual tranche, ranging from 2034 to 2047, which represents the outside expiration date for the sublease rights to the towers in that tranche. The purchase price for each tranche is a fixed amount stated in the lease for such tranche plus the fair market value of certain alterations made to the related towers. The aggregate purchase option price for the towers leased and subleased is approximately $5.0 billion. Verizon will occupy the sites as a tenant for an initial term of ten years with eight optional successive five-year terms; each such term shall be governed by standard master lease agreement terms established as a part of the transaction. AT&T Transaction—The Company has an agreement with SBC Communications Inc., a predecessor entity to AT&T, that currently provides for the lease or sublease of approximately 2,270 towers commencing between December 2000 and August 2004. Substantially all of the towers are part of the securitization transactions completed in March 2013 and March 2018. The average term of the lease or sublease for all sites at the inception of the agreement was approximately 27 years, assuming renewals or extensions of the underlying ground leases for the sites. The Company has the option to purchase the sites subject to the applicable lease or sublease upon its expiration. Each tower is assigned to an annual tranche, ranging from 2013 to 2032, which represents the outside expiration date for the sublease rights to that tower. The purchase price for each site is a fixed amount stated in the lease for that site plus the fair market value of certain alterations made to the related tower by AT&T. As of September 30, 2019, the Company has purchased an aggregate of 154 of the subleased towers upon expiration of the applicable agreement. The aggregate purchase option price for the remaining towers leased and subleased is $955.7 million and will accrete at a rate of 10% per annum through the applicable expiration of the lease or sublease of a site. For all such sites, AT&T has the right to continue to lease the reserved space through June 30, 2020 at the then-current monthly fee, which shall escalate in accordance with the standard master lease agreement for the remainder of AT&T’s tenancy. Thereafter, AT&T shall have the right to renew such lease for up to four successive five-year terms. ALLTEL Transaction—In December 2000, the Company entered into an agreement with ALLTEL Communications, LLC, a predecessor entity to Verizon Wireless, to acquire towers through a 15-year sublease agreement. Pursuant to the agreement, as amended, with Verizon Wireless, the Company acquired rights to approximately 1,800 towers in tranches between April 2001 and March 2002. The Company had the option to purchase each tower at the expiration of the applicable sublease. During the year ended December 31, 2016, the Company exercised the purchase options for 1,523 towers in a single closing and provided notice to the tower owner, Verizon’s assignee, of its intent to exercise the purchase options related to the remaining 243 towers. On August 30, 2019, the Company purchased the remaining 243 towers for an aggregate purchase price of $43.0 million in cash in lieu of shares of the Company’s common stock. Other Contingencies—The Company is subject to income tax and other taxes in the geographic areas where it operates, and periodically receives notifications of audits, assessments or other actions by taxing authorities. Taxing authorities may issue notices or assessments while audits are being conducted. In certain jurisdictions, taxing authorities may issue assessments with minimal examination. These notices and assessments do not represent amounts that the Company is obligated to pay and are often not reflective of the actual tax liability for which the Company will ultimately be liable. In the process of responding to assessments of taxes that the Company believes are not enforceable, the Company avails itself of both administrative and judicial remedies. The Company evaluates the circumstances of each notification or assessment based on the information available and, in those instances in which the Company does not anticipate a successful defense of positions taken in its tax filings, a liability is recorded in the appropriate amount based on the underlying assessment. On December 5, 2016, the Company received an income tax assessment of Essar Telecom Infrastructure Private Limited (“ETIPL”) from the India Income Tax Department (the “Tax Department”) for the fiscal year ending 2008 in the amount of INR 4.75 billion ($69.8 million on the date of assessment) related to capital contributions. The Company challenged the assessment before the Office of Commissioner of Income Tax - Appeals, which ruled in the Company’s favor in January 2018. However, the Tax Department has appealed this ruling at a higher appellate authority. The Company estimates that there is a more likely than not probability that the Company’s position will be sustained upon appeal. Accordingly, no liability has been recorded. Additionally, the assessment was made with respect to transactions that took place in the tax year commencing in 2007, prior to the Company’s acquisition of ETIPL. Under the Company’s definitive acquisition agreement of ETIPL, the seller is obligated to indemnify and defend the Company with respect to any tax-related liability that may arise from activities prior to March 31, 2010.

ACQUISITIONS

9 Months Ended

Sep. 30, 2019

Business Combinations [Abstract]

ACQUISITIONS

Impact of current year acquisitions—The Company typically acquires communications sites from wireless carriers or other tower operators and subsequently integrates those sites into its existing portfolio of communications sites. The financial results of the Company’s acquisitions have been included in the Company’s consolidated statements of operations for the three and nine months ended September 30, 2019 from the date of the respective acquisition. The date of acquisition, and by extension the point at which the Company begins to recognize the results of an acquisition, may depend on, among other things, the receipt of contractual consents, the commencement and extent of leasing arrangements and the timing of the transfer of title or rights to the assets, which may be accomplished in phases. Sites acquired from communications service providers may never have been operated as a business and may instead have been utilized solely by the seller as a component of its network infrastructure. An acquisition may or may not involve the transfer of business operations or employees.

The Company evaluates each of its acquisitions under the accounting guidance framework to determine whether to treat an acquisition as an asset acquisition or a business combination. For those transactions treated as asset acquisitions, the purchase price is allocated to the assets acquired, with no recognition of goodwill.

For those acquisitions accounted for as business combinations, the Company recognizes acquisition and merger related expenses in the period in which they are incurred and services are received; for transactions accounted for as asset acquisitions, these costs are capitalized as part of the purchase price. Acquisition and merger related costs may include finder’s fees, advisory, legal, accounting, valuation and other professional or consulting fees and general administrative costs directly related to completing the transaction. Integration costs include incremental and non-recurring costs necessary to convert data, retain employees and otherwise enable the Company to operate acquired businesses or assets efficiently. The Company records acquisition and merger related expenses for business combinations, as well as integration costs for all acquisitions, in Other operating expenses in the consolidated statements of operations.

During the three and nine months ended September 30, 2019 and 2018, the Company recorded acquisition and merger related expenses for business combinations and non-capitalized asset acquisition costs and integration costs as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Acquisition and merger related expenses	$	5.8	$	0.9	$	11.6	$	6.8
Integration costs	$	1.6	$	9.8	$	7.8	$	15.0

The Company also received $13.1 million related to pre-acquisition contingencies and settlements during the nine months ended September 30, 2019.

2019 Transactions

The estimated aggregate impact of the acquisitions completed in 2019 on the Company’s revenues and gross margin for the three months ended September 30, 2019 was approximately $5.3 million and $3.9 million, respectively, and for the nine months ended September 30, 2019 was approximately $7.9 million and $5.7 million, respectively. The revenues and gross margin amounts also reflect incremental revenues from the addition of new tenants to such sites subsequent to the transaction date.

U.S. Acquisition—On August 30, 2019, the Company acquired approximately 400 towers and other related property interests in the United States for an aggregate total purchase price of $483.9 million. This acquisition was accounted for as an asset acquisition.

Other Acquisitions—During the nine months ended September 30, 2019, the Company acquired a total of 582 communications sites in the United States, Colombia, Mexico, Paraguay and Peru, as well as other communications infrastructure assets, for an aggregate purchase price of $183.8 million. The majority of these acquisitions were accounted for as asset acquisitions.

The following table summarizes the allocations of the purchase prices for the fiscal year 2019 acquisitions based upon their estimated fair value at the date of acquisition:



	U.S. Acquisition			Other (1)
Current assets	$	4.0		$	7.9
Property and equipment	97.7			57.7
Intangible assets (2):
Tenant-related intangible assets	271.3			62.0
Network location intangible assets	110.9			27.0
Other intangible assets	—			0.8
Other non-current assets	55.5			7.8
Current liabilities	(2.4		)	(1.0		)
Deferred tax liability	—			—
Other non-current liabilities	(53.1		)	(12.7		)
Net assets acquired	483.9			149.5
Goodwill (3)	—			34.3
Fair value of net assets acquired	483.9			183.8
Debt assumed	—			—
Purchase price	$	483.9		$	183.8

_______________


(1)	Includes 106 sites in Peru held pursuant to long-term finance leases.


(2)	Tenant-related intangible assets and network location intangible assets are amortized on a straight-line basis over periods of up to 20 years.


(3)	The Company expects goodwill to be deductible for tax purposes.

In addition to the acquisitions discussed above, on August 30, 2019, the Company purchased 243 towers related to the ALLTEL transaction described in note 15 for an aggregate purchase price of $43.0 million.

Other Signed Acquisitions

Eaton Towers—On May 30, 2019, the Company entered into a definitive agreement to acquire 100% of the outstanding shares of Eaton Towers Holding Limited (“Eaton Towers”), which owns and operates approximately 5,500 communications sites across five African markets. The total consideration for the transaction, including the Company’s assumption of existing Eaton Towers debt, is approximately $1.85 billion, subject to customary closing adjustments. The transaction is expected to close by the end of 2019, subject to customary closing conditions, including the satisfaction of regulatory approvals. Subject to the closing of the Eaton Towers transaction, the Company anticipates acquiring the interests of MTN in each of the Company’s joint ventures in Ghana and Uganda.

2018 Transactions

During the nine months ended September 30, 2019, the allocation of the purchase price for the acquisition of Idea Cellular Infrastructure Services Limited was finalized with no material post-closing adjustments. During the nine months ended September 30, 2019, there were no material post-closing adjustments that impacted other 2018 acquisitions.

Pro Forma Consolidated Results (Unaudited)

The following table presents the unaudited pro forma financial results as if the 2019 acquisitions had occurred on January 1, 2018 and the 2018 acquisitions had occurred on January 1, 2017. The pro forma results do not include any anticipated cost synergies, costs or other integration impacts. Accordingly, such pro forma amounts are not necessarily indicative of the results that actually would have occurred had the transactions been completed on the date indicated, nor are they indicative of the future operating results of the Company.



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Pro forma revenues	$	1,957.7	$	1,813.4	$	5,676.0	$	5,499.9
Pro forma net income attributable to American Tower Corporation common stockholders	$	497.7	$	363.3	$	1,321.9	$	937.8
Pro forma net income per common share amounts:
Basic net income attributable to American Tower Corporation common stockholders	$	1.12	$	0.82	$	2.99	$	2.14
Diluted net income attributable to American Tower Corporation common stockholders	$	1.12	$	0.82	$	2.97	$	2.12

BUSINESS SEGMENTS

9 Months Ended

Sep. 30, 2019

Segment Reporting [Abstract]

BUSINESS SEGMENTS

The Company’s primary business is leasing space on multitenant communications sites to wireless service providers, radio and television broadcast companies, wireless data providers, government agencies and municipalities and tenants in a number of other industries. This business is referred to as the Company’s property operations, which as of September 30, 2019, consisted of the following:


•	U.S.: property operations in the United States;


•	Asia: property operations in India;


•	Europe, Middle East and Africa (“EMEA”): property operations in France, Germany, Ghana, Kenya, Nigeria, South Africa and Uganda; and


•	Latin America: property operations in Argentina, Brazil, Chile, Colombia, Costa Rica, Mexico, Paraguay and Peru.

The Company’s services segment offers tower-related services in the United States, including AZP and structural analysis, which primarily support its site leasing business, including the addition of new tenants and equipment on its sites. The services segment is a strategic business unit that offers different services from, and requires different resources, skill sets and marketing strategies than, the property operating segments.

The accounting policies applied in compiling segment information below are similar to those described in note 1 to the Company’s consolidated financial statements included in the 2018 Form 10-K and as updated in note 1 above. Among other factors, in evaluating financial performance in each business segment, management uses segment gross margin and segment operating profit. The Company defines segment gross margin as segment revenue less segment operating expenses excluding stock-based compensation expense recorded in costs of operations; Depreciation, amortization and accretion; Selling, general, administrative and development expense; and Other operating expenses. The Company defines segment operating profit as segment gross margin less Selling, general, administrative and development expense attributable to the segment, excluding stock-based compensation expense and corporate expenses. For reporting purposes, for periods through September 30, 2018, the Latin America property segment gross margin and segment operating profit also include Interest income (expense), TV Azteca, net. These measures of segment gross margin and segment operating profit are also before Interest income, Interest expense, Gain (loss) on retirement of long-term obligations, Other income (expense), Net income (loss) attributable to noncontrolling interests and Income tax benefit (provision). The categories of expenses indicated above, such as depreciation, have been excluded from segment operating performance as they are not considered in the review of information or the evaluation of results by management. There are no significant revenues resulting from transactions between the Company’s operating segments.

All intercompany transactions are eliminated to reconcile segment results and assets to the consolidated statements of operations and consolidated balance sheets.

Summarized financial information concerning the Company’s reportable segments for the three and nine months ended September 30, 2019 and 2018 is shown in the following tables. The “Other” column (i) represents amounts excluded from specific segments, such as business development operations, stock-based compensation expense and corporate expenses included in Selling, general, administrative and development expense; Other operating expenses; Interest income; Interest expense; Gain (loss) on retirement of long-term obligations; and Other income (expense), and (ii) reconciles segment operating profit to Income from continuing operations before income taxes.



	Property								Total Property		Services		Other		Total
Three Months Ended September 30, 2019	U.S.		Asia		EMEA		Latin America		Total Property		Services		Other		Total
Segment revenues	$	1,095.9	$	312.5	$	181.5	$	331.7	$	1,921.6	$	32.0			$	1,953.6
Segment operating expenses (1)	207.5		177.9		58.6		103.6		547.6		11.7				559.3
Segment gross margin	888.4		134.6		122.9		228.1		1,374.0		20.3				1,394.3
Segment selling, general, administrative and development expense (1)	44.5		33.1		19.7		23.5		120.8		3.4				124.2
Segment operating profit	$	843.9	$	101.5	$	103.2	$	204.6	$	1,253.2	$	16.9			$	1,270.1
Stock-based compensation expense													$	23.5	23.5
Other selling, general, administrative and development expense													40.8		40.8
Depreciation, amortization and accretion													442.8		442.8
Other expense (2)													221.0		221.0
Income from continuing operations before income taxes															$	542.0
Total assets	$	22,653.2	$	5,324.9	$	3,626.6	$	7,129.2	$	38,733.9	$	55.8	$	517.5	$	39,307.2

_______________


(1)	Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $0.6 million and $22.9 million, respectively.


(2)	Primarily includes interest expense and $14.0 million in impairment charges.



	Property								Total Property		Services		Other		Total
Three Months Ended September 30, 2018	U.S.		Asia		EMEA		Latin America		Total Property		Services		Other		Total
Segment revenues	$	957.7	$	323.1	$	166.6	$	304.2	$	1,751.6	$	33.9			$	1,785.5
Segment operating expenses (1)	193.3		194.7		57.5		96.8		542.3		13.4				555.7
Interest income, TV Azteca, net	—		—		—		0.6		0.6		—				0.6
Segment gross margin	764.4		128.4		109.1		208.0		1,209.9		20.5				1,230.4
Segment selling, general, administrative and development expense (1)	37.9		13.5		16.2		20.7		88.3		6.3				94.6
Segment operating profit	$	726.5	$	114.9	$	92.9	$	187.3	$	1,121.6	$	14.2			$	1,135.8
Stock-based compensation expense													$	43.8	43.8
Other selling, general, administrative and development expense													40.5		40.5
Depreciation, amortization and accretion													448.9		448.9
Other expense (2)													212.8		212.8
Income from continuing operations before income taxes															$	389.8
Total assets	$	18,664.5	$	5,093.7	$	3,272.7	$	5,677.5	$	32,708.4	$	50.6	$	318.2	$	33,077.2

_______________


(1)	Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $1.0 million and $42.8 million, respectively.


(2)	Primarily includes interest expense and $1.8 million in impairment charges.



	Property								Total Property		Services		Other		Total
Nine Months Ended September 30, 2019	U.S.		Asia		EMEA		Latin America		Total Property		Services		Other		Total
Segment revenues	$	3,089.4	$	922.5	$	534.0	$	1,010.6	$	5,556.5	$	100.1			$	5,656.6
Segment operating expenses (1)	595.4		544.2		178.9		310.5		1,629.0		35.5				1,664.5
Segment gross margin	2,494.0		378.3		355.1		700.1		3,927.5		64.6				3,992.1
Segment selling, general, administrative and development expense (1)	128.4		77.4		58.1		75.0		338.9		8.8				347.7
Segment operating profit	$	2,365.6	$	300.9	$	297.0	$	625.1	$	3,588.6	$	55.8			$	3,644.4
Stock-based compensation expense													$	87.9	87.9
Other selling, general, administrative and development expense													117.3		117.3
Depreciation, amortization and accretion													1,328.6		1,328.6
Other expense (2)													663.1		663.1
Income from continuing operations before income taxes															$	1,447.5

_______________


(1)	Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $2.1 million and $85.8 million, respectively.


(2)	Primarily includes interest expense and $45.1 million in impairment charges.



	Property									Total Property			Services		Other		Total
Nine Months Ended September 30, 2018	U.S.		Asia		EMEA		Latin America			Total Property			Services		Other		Total
Segment revenues	$	2,846.1	$	904.0	$	507.5	$	953.8		$	5,211.4		$	96.8			$	5,308.2
Segment operating expenses (1)	578.4		532.7		175.1		309.5			1,595.7			38.5				1,634.2
Interest expense, TV Azteca, net	—		—		—		(0.1		)	(0.1		)	—				(0.1		)
Segment gross margin	2,267.7		371.3		332.4		644.2			3,615.6			58.3				3,673.9
Segment selling, general, administrative and development expense (1)	117.1		72.8		50.6		64.4			304.9			12.7				317.6
Segment operating profit	$	2,150.6	$	298.5	$	281.8	$	579.8		$	3,310.7		$	45.6			$	3,356.3
Stock-based compensation expense															$	111.3	111.3
Other selling, general, administrative and development expense															114.5		114.5
Depreciation, amortization and accretion															1,344.9		1,344.9
Other expense (2)															828.3		828.3
Income from continuing operations before income taxes																	$	957.3

_______________


(1)	Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $2.7 million and $108.6 million, respectively.

(2)

Primarily includes interest expense and $182.4 million in impairment charges.

SUBSEQUENT EVENTS	9 Months Ended
SUBSEQUENT EVENTS	Sep. 30, 2019
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS 2.750% Senior Notes and 3.700% Senior Notes Offering—On October 3, 2019, the Company completed a registered public offering of $750.0 million aggregate principal amount of 2.750% senior unsecured notes due 2027 (the “2.750% Notes”) and $600.0 million aggregate principal amount of 3.700% senior unsecured notes due 2049 (the “3.700% Notes”). The net proceeds from this offering were approximately $1,334.2 million, after deducting commissions and estimated expenses. The Company used the net proceeds to repay existing indebtedness under the 2013 Credit Facility and the 2019 Term Loan. The 2.750% Notes will mature on January 15, 2027 and bear interest at a rate of 2.750% per annum. The 3.700% Notes will mature on October 15, 2049 and bear interest at a rate of 3.700% per annum. Accrued and unpaid interest on the 2.750% Notes will be payable in U.S. Dollars semi-annually in arrears on January 15 and July 15 of each year, beginning on January 15, 2020. Accrued and unpaid interest on the 3.700% Notes will be payable in U.S. Dollars semi-annually in arrears on April 15 and October 15 of each year, beginning on April 15, 2020. Interest on the 2.750% Notes and the 3.700% Notes will accrue from October 3, 2019 and will be computed on the basis of a 360-day year comprised of twelve 30-day months. The Company may redeem the 2.750% Notes and the 3.700% Notes at any time, in whole or in part, at a redemption price equal to 100% of the principal amount of the 2.750% Notes and the 3.700% Notes plus a make-whole premium, together with accrued interest to the redemption date. If the Company redeems the 2.750% Notes on or after November 15, 2026 or the 3.700% Notes on or after April 15, 2049, the Company will not be required to pay a make-whole premium. In addition, if the Company undergoes a change of control and corresponding ratings decline, each as defined in the supplemental indenture, it may be required to repurchase all of the 2.750% Notes and the 3.700% Notes at a purchase price equal to 101% of the principal amount of such notes, plus accrued and unpaid interest (including additional interest, if any), up to but not including the repurchase date. The 2.750% Notes and the 3.700% Notes rank equally with all of the Company’s other senior unsecured debt and are structurally subordinated to all existing and future indebtedness and other obligations of its subsidiaries. The supplemental indenture contains certain covenants that restrict the Company’s ability to merge, consolidate or sell assets and its (together with its subsidiaries’) ability to incur liens. These covenants are subject to a number of exceptions, including that the Company and its subsidiaries may incur certain liens on assets, mortgages or other liens securing indebtedness if the aggregate amount of indebtedness secured by such liens does not exceed 3.5x Adjusted EBITDA, as defined in the supplemental indenture.

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	The accompanying consolidated and condensed consolidated financial statements have been prepared by American Tower Corporation (together with its subsidiaries, “ATC” or the “Company”) pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The financial information included herein is unaudited. However, the Company believes that all adjustments, which are of a normal and recurring nature, considered necessary for a fair presentation of its financial position and results of operations for such periods have been included herein. The consolidated and condensed consolidated financial statements and related notes should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 (the “2018 Form 10-K”). The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of the results that may be expected for the entire year.
Principles of Consolidation and Basis of Presentation	Principles of Consolidation and Basis of Presentation—The accompanying consolidated and condensed consolidated financial statements include the accounts of the Company and those entities in which it has a controlling interest. Investments in entities that the Company does not control are accounted for using the equity method or as investments in equity securities, depending upon the Company’s ability to exercise significant influence over operating and financial policies. All intercompany accounts and transactions have been eliminated.
Lease	Lease—The new lease standard requires leases to be accounted for using a right-of-use model, which recognizes that, at the date of commencement, a lessee has a financial obligation to make lease payments to the lessor for the right to use the underlying asset during the lease term. The lessee recognizes a corresponding right-of-use asset related to this right. On January 1, 2019, the Company elected to adopt the new lease standard using the modified retrospective method applied to lease arrangements that were in place on the transition date. Results for reporting periods beginning January 1, 2019 are presented under the new standard, while prior-period amounts are not adjusted and continue to be reported in accordance with accounting under the previously applicable guidance. The Company elected certain available practical expedients which permit the adopter to not reassess certain items upon adoption, including: (i) whether any existing contracts are or contain leases, (ii) the classification of existing leases and (iii) initial direct costs for existing leases. The Company also elected the practical expedient related to easements, which permits carryforward accounting treatment for land easements on existing agreements. The Company recorded a net increase to opening Distributions in excess of earnings in its consolidated balance sheet of $24.7 million as of January 1, 2019 due to the cumulative impact of adopting the new lease standard. This adjustment related to right-of-use asset impairments. The Company also recorded a lease liability of $6.9 billion and a corresponding right-of-use asset of $7.1 billion upon adoption of the new lease standard. Those rights and obligations are primarily related to operating leases for ground space underneath the Company’s communications sites. The right-of-use assets recorded include, among other items, amounts previously classified as prepaid rent, deferred lease acquisition costs, fair value adjustments on acquired leases and long-term deferred rent obligations. Finance leases, which primarily relate to towers, equipment and vehicles, were largely unchanged. There was no significant change to the Company’s consolidated statements of operations resulting from the adoption of this standard. The Company did not elect the practical expedient for short-term leases, which permits an adopter to not apply the lease standard to leases with a remaining maturity of one year or less, and applied the new lease accounting standard to all leases, including short-term leases. In conjunction with the adoption of the new lease accounting guidance, the Company applied the lessor and lessee practical expedient and no longer separates lease and non-lease components within a lease agreement when the timing and pattern of revenue recognition for the components are the same and the combined single lease component is classified as an operating lease. Certain amounts, such as power and fuel and common area maintenance, which were previously reported as non-lease revenue, are now accounted for as lease revenue. Accordingly, the Company has reclassified certain prior-period amounts within its disclosures.
Revenue	Revenue—Most of the Company’s revenue is derived from leasing arrangements and is accounted for as lease revenue unless the timing and pattern of revenue recognition differs from the lease components. Revenue related to distributed antenna system (“DAS”) networks and fiber results from agreements with tenants that are not leases. Non-lease revenue—Non-lease revenue consists primarily of revenue generated from DAS networks, fiber and other property related revenue. DAS networks and fiber arrangements require that the Company provide the tenant the right to use the applicable communications infrastructure. Performance obligations are satisfied over time for the duration of the arrangements. Other property related revenue streams, which include site inspections, are not material on either an individual or consolidated basis. Services revenue—The Company offers tower-related services in the United States. These services include site acquisition, zoning and permitting (“AZP”) and structural analysis. There is a single performance obligation related to AZP and revenue is recognized over time based on milestones achieved, which are determined based on costs expected to be incurred. Structural analysis services may have more than one performance obligation, contingent upon the number of contracted services. Revenue is recognized at the point in time the services are completed.
Accounting Standards Updates	Accounting Standards Updates In June 2016, the Financial Accounting Standards Board (the “FASB”) issued guidance that modifies how entities measure credit losses on most financial instruments. The new guidance replaces the current "incurred loss" model with an "expected credit loss" model that requires consideration of a broader range of information to estimate expected credit losses over the lifetime of the asset. The new guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, and will be applied using a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of the effective date. Operating lease receivables are not within the scope of this guidance. The Company is finalizing its analysis of the impact of this guidance on its financial statements and does not expect the adoption of this guidance to have a material impact on the Company’s financial statements. In January 2017, the FASB issued guidance on accounting for goodwill impairments. The guidance eliminates Step 2 from the goodwill impairment test and requires, among other things, recognition of an impairment loss when the carrying value of a reporting unit exceeds its fair value. The loss recognized is limited to the total amount of goodwill allocated to that reporting unit. The guidance is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company does not expect the adoption of this guidance to have a material impact on the Company’s financial statements. In August 2018, the FASB issued guidance on the accounting for implementation costs incurred in a cloud computing arrangement that is a service contract. This guidance aligns the accounting for costs incurred to implement a cloud computing arrangement that is a service arrangement with the guidance on capitalizing costs associated with developing or obtaining internal-use software. The Company adopted this guidance prospectively on July 1, 2019. The adoption of this guidance did not have a material impact on the Company’s financial statements.

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Tables)

9 Months Ended

Sep. 30, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Reconciliation of Cash and Cash Equivalents and Restricted Cash

The reconciliation of cash and cash equivalents and restricted cash reported within the applicable balance sheet that sum to the total of the same such amounts shown in the statement of cash flows is as follows:



	Nine Months Ended September 30,
	2019		2018
Cash and cash equivalents	$	1,352.6	$	1,026.5
Restricted cash	95.7		266.8
Total cash and cash equivalents and restricted cash	$	1,448.3	$	1,293.3

Summary of Revenue Disaggregated by Source and Geography

A summary of revenue disaggregated by source and geography is as follows:



Three Months Ended September 30, 2019	U.S.		Asia		EMEA		Latin America		Total
Non-lease property revenue	$	66.7	$	2.2	$	2.3	$	34.1	$	105.3
Services revenue	32.0		—		—		—		32.0
Total non-lease revenue	$	98.7	$	2.2	$	2.3	$	34.1	$	137.3
Property lease revenue	1,029.2		310.3		179.2		297.6		1,816.3
Total revenue	$	1,127.9	$	312.5	$	181.5	$	331.7	$	1,953.6



Three Months Ended September 30, 2018 (1)	U.S.		Asia		EMEA		Latin America		Total
Non-lease property revenue	$	62.4	$	1.6	$	0.4	$	23.6	$	88.0
Services revenue	33.9		—		—		—		33.9
Total non-lease revenue	$	96.3	$	1.6	$	0.4	$	23.6	$	121.9
Property lease revenue	895.3		321.5		166.2		280.6		1,663.6
Total revenue	$	991.6	$	323.1	$	166.6	$	304.2	$	1,785.5

_______________


(1)	Prior-period amounts adjusted with the adoption of the new lease accounting guidance, as applicable.



Nine Months Ended September 30, 2019	U.S.		Asia		EMEA		Latin America		Total
Non-lease property revenue	$	186.3	$	6.7	$	5.8	$	103.9	$	302.7
Services revenue	100.1		—		—		—		100.1
Total non-lease revenue	$	286.4	$	6.7	$	5.8	$	103.9	$	402.8
Property lease revenue	2,903.1		915.8		528.2		906.7		5,253.8
Total revenue	$	3,189.5	$	922.5	$	534.0	$	1,010.6	$	5,656.6



Nine Months Ended September 30, 2018 (1)	U.S.		Asia		EMEA		Latin America		Total
Non-lease property revenue	$	190.3	$	5.0	$	1.1	$	71.9	$	268.3
Services revenue	96.8		—		—		—		96.8
Total non-lease revenue	$	287.1	$	5.0	$	1.1	$	71.9	$	365.1
Property lease revenue	2,655.8		899.0		506.4		881.9		4,943.1
Total revenue	$	2,942.9	$	904.0	$	507.5	$	953.8	$	5,308.2

_______________

(1)

Prior-period amounts adjusted with the adoption of the new lease accounting guidance, as applicable.

Information About Receivables, Contract Assets and Contract Liabilities From Contracts With Tenants

Information about receivables, contract assets and contract liabilities from non-lease contracts with tenants is as follows:



	September 30, 2019		December 31, 2018 (1)
Accounts receivable	$	94.0	$	92.6
Prepaids and other current assets	10.0		7.7
Notes receivable and other non-current assets	26.0		22.2
Unearned revenue (2)	37.9		35.0
Other non-current liabilities (3)	68.8		54.1

_______________


(1)	Prior-period amounts adjusted with the adoption of the new lease accounting guidance, as applicable.


(2)	Excludes $56.1 million and $55.0 million of capital contributions related to DAS networks as of September 30, 2019 and December 31, 2018, respectively.

(3)

Excludes $301.6 million and $313.6 million of capital contributions related to DAS networks as of September 30, 2019 and December 31, 2018, respectively.

PROPERTY AND EQUIPMENT (Tables)

9 Months Ended

Sep. 30, 2019

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

Property and equipment (including assets held under financing leases) consisted of the following:



	Estimated Useful Lives (years) (1)	As of
	Estimated Useful Lives (years) (1)	September 30, 2019			December 31, 2018
Towers	Up to 20	$	13,044.9		$	12,777.9
Equipment (2)	2 - 20	1,807.1			1,667.3
Buildings and improvements	3 - 32	636.2			628.5
Land and improvements (3)	Up to 20	2,435.4			2,285.4
Construction-in-progress		378.7			358.1
Total		18,302.3			17,717.2
Less accumulated depreciation		(7,019.1		)	(6,470.1		)
Property and equipment, net		$	11,283.2		$	11,247.1

_______________


(1)	Assets on leased land are depreciated over the shorter of the estimated useful life of the asset or the term of the corresponding ground lease taking into consideration lease renewal options and residual value.


(2)	Includes fiber and DAS assets.


(3)	Estimated useful lives apply to improvements only.

Schedule of Finance Lease Assets Included In Property Plant And Equipment

As of December 31, 2018, property and equipment included $4,369.5 million of capital lease assets with related equipment and improvements and $1,016.2 million of accumulated depreciation.

Information about finance lease-related balances is as follows:



		As of
Finance leases:	Classification	September 30, 2019
Property and equipment	Towers	$	2,706.9
Accumulated depreciation		(1,039.8		)
Property and equipment, net		$	1,667.1

Property and equipment	Buildings and improvements	$	171.4
Accumulated depreciation		(64.8		)
Property and equipment, net		$	106.6

Property and equipment	Land	$	152.1

Property and equipment	Equipment	$	45.0
Accumulated depreciation		(11.9		)
Property and equipment, net		$	33.1

LEASES (Tables)

9 Months Ended

Sep. 30, 2019

Leases [Abstract]

Lessor, Maturities of Minimum Rental Receipts Expected Under Non-cancellable Operating Leases Lease, Payments to be Received, Maturity

Future minimum rental receipts expected under non-cancellable operating lease agreements as of September 30, 2019 were as follows:



Fiscal Year	Amount (1)
Remainder of 2019	$	1,394.7
2020	5,645.9
2021	5,442.0
2022	4,846.6
2023	4,710.8
Thereafter	24,225.4
Total	$	46,265.4

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Future minimum rental receipts expected under non-cancellable operating lease agreements in effect at December 31, 2018 were as follows:



Year Ended December 31,	Amount (1)
2019	$	5,251.2
2020	5,062.2
2021	4,676.1
2022	3,754.6
2023	3,457.3
Thereafter	12,641.1
Total	$	34,842.5

_______________


(1)	Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Schedule of Information About Other Lease-related Balances

Information about other lease-related balances as of September 30, 2019 is as follows:



Operating leases:
Right-of-use asset	$	7,214.7

Current portion of lease liability	$	475.1
Lease liability	6,448.0
Total operating lease liability	$	6,923.1

Finance leases:
Current portion of lease liability	$	7.1
Lease liability	23.1
Total finance lease liability	$	30.2

Components of Operating Lease Cost

The weighted-average remaining lease terms and incremental borrowing rates as of September 30, 2019 are as follows:



Operating leases:
Weighted-average remaining lease term (years)	13.3
Weighted-average incremental borrowing rate	6.3	%

Finance leases:
Weighted-average remaining lease term (years)	15.0
Weighted-average incremental borrowing rate	6.2	%

The following table sets forth the components of lease cost for the three and nine months ended September 30, 2019:



	Three Months Ended September 30, 2019		Nine Months Ended September 30, 2019
Operating lease cost	$	249.5	$	760.3
Variable lease costs not included in lease liability (1)	67.7		190.8

_______________


(1)	Includes property tax paid on behalf of the landlord.

Supplemental cash flow information for the nine months ended September 30, 2019 is as follows:



Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	(701.9	)
Operating cash flows from finance leases	$	(1.1	)
Financing cash flows from finance leases	$	(16.4	)

Non-cash items:
New operating leases	$	224.8
Operating lease modifications and reassessments	$	338.9

Maturity of Operating Lease Liabilities

Maturities of operating and finance lease liabilities as of September 30, 2019 were as follows:



Fiscal Year	Operating Lease (1)			Finance Lease (1)
Remainder of 2019	$	217.4		$	2.8
2020	876.0			7.6
2021	860.4			4.9
2022	822.4			4.0
2023	785.4			2.6
Thereafter	6,735.8			45.5
Total lease payments	10,297.4			67.4
Less amounts representing interest	(3,374.3		)	(37.2		)
Total lease liability	6,923.1			30.2
Less current portion of lease liability	(475.1		)	(7.1		)
Non-current lease liability	$	6,448.0		$	23.1

_______________

(1)

Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Maturity of Finance Lease Liabilities

Maturities of operating and finance lease liabilities as of September 30, 2019 were as follows:



Fiscal Year	Operating Lease (1)			Finance Lease (1)
Remainder of 2019	$	217.4		$	2.8
2020	876.0			7.6
2021	860.4			4.9
2022	822.4			4.0
2023	785.4			2.6
Thereafter	6,735.8			45.5
Total lease payments	10,297.4			67.4
Less amounts representing interest	(3,374.3		)	(37.2		)
Total lease liability	6,923.1			30.2
Less current portion of lease liability	(475.1		)	(7.1		)
Non-current lease liability	$	6,448.0		$	23.1

_______________

(1)

Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Schedule of Future Minimum Rental Payments for Operating Leases

Future minimum rental payments under non-cancellable operating leases as of December 31, 2018 is as follows:



Year Ended December 31,	Amount (1)
2019	$	926.0
2020	904.2
2021	879.8
2022	834.2
2023	792.6
Thereafter	6,173.1
Total	$	10,509.9

_______________

(1)

Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

Schedule of Future Minimum Lease Payments for Capital Leases

Future minimum rental payments under capital leases in effect as of December 31, 2018 were as follows:



Year Ended December 31,	Amount (1)
2019	$	40.7
2020	32.7
2021	27.8
2022	23.7
2023	19.2
Thereafter	117.5
Total	261.6
Less amounts representing interest	(82.1		)
Present value of capital lease obligations	$	179.5

_______________

(1)

Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)

9 Months Ended

Sep. 30, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Changes in the carrying value of goodwill

The changes in the carrying value of goodwill for each of the Company’s business segments were as follows:



	Property											Services		Total
	U.S.		Asia			EMEA			Latin America			Services		Total
Balance as of January 1, 2019	$	3,382.5	$	1,045.5		$	381.3		$	690.6		$	2.0	$	5,501.9
Additions and adjustments (1)	33.5		—			—			—			—		33.5
Effect of foreign currency translation	—		(16.3		)	(16.8		)	(20.9		)	—		(54.0		)
Balance as of September 30, 2019	$	3,416.0	$	1,029.2		$	364.5		$	669.7		$	2.0	$	5,481.4

_______________


(1)	Additions consist of $34.3 million resulting from 2019 acquisitions offset by $0.8 million from revisions to prior-year acquisitions due to measurement period adjustments.

Intangible assets subject to amortization

The Company’s other intangible assets subject to amortization consisted of the following:



		As of September 30, 2019							As of December 31, 2018
	Estimated Useful Lives (years)	Gross Carrying Value		Accumulated Amortization			Net Book Value		Gross Carrying Value		Accumulated Amortization			Net Book Value
Acquired network location intangibles (1)	Up to 20	$	4,832.7	$	(1,863.2	)	$	2,969.5	$	4,780.3	$	(1,704.9	)	$	3,075.4
Acquired tenant-related intangibles	15-20	11,359.2		(3,517.3		)	7,841.9		11,156.5		(3,147.2		)	8,009.3
Acquired licenses and other intangibles	3-20	103.9		(19.5		)	84.4		104.1		(14.5		)	89.6
Total other intangible assets		$	16,295.8	$	(5,400.0	)	$	10,895.8	$	16,040.9	$	(4,866.6	)	$	11,174.3

_______________

(1)

Acquired network location intangibles are amortized over the shorter of the term of the corresponding ground lease, taking into consideration lease renewal options and residual value, or up to 20 years, as the Company considers these intangibles to be directly related to the tower assets.

Expected future amortization expenses

Based on current exchange rates, the Company expects to record amortization expense as follows over the remaining current year and the five subsequent years:



Fiscal Year	Amount
Remainder of 2019	$	199.0
2020	777.8
2021	761.7
2022	757.7
2023	753.8
2024	750.8

LONG-TERM OBLIGATIONS (Tables)

9 Months Ended

Sep. 30, 2019

Debt Disclosure [Abstract]

Schedule of long-term obligations

Outstanding amounts under the Company’s long-term obligations, reflecting discounts, premiums, debt issuance costs and fair value adjustments due to interest rate swaps consisted of the following:



	As of
	September 30, 2019			December 31, 2018			Maturity Date
2018 Term Loan (1) (2)	$	—		$	1,499.8		March 29, 2019
2019 Term Loan (1)	1,299.8			—			February 13, 2020
2013 Credit Facility (1)	1,122.0			1,875.0			June 28, 2022
2013 Term Loan (1)	995.5			994.8			January 31, 2024
2014 Credit Facility (1)	—			—			January 31, 2024
3.40% senior notes (3)	—			1,000.0			February 15, 2019
2.800% senior notes	749.0			747.8			June 1, 2020
5.050% senior notes (4)	—			698.7			September 1, 2020
3.300% senior notes	748.2			747.2			February 15, 2021
3.450% senior notes	647.3			646.3			September 15, 2021
5.900% senior notes	498.8			498.4			November 1, 2021
2.250% senior notes	592.0			572.7			January 15, 2022
4.70% senior notes	698.0			697.4			March 15, 2022
3.50% senior notes	993.8			992.6			January 31, 2023
3.000% senior notes	708.0			687.5			June 15, 2023
5.00% senior notes	1,001.8			1,002.1			February 15, 2024
3.375% senior notes	644.1			—			May 15, 2024
2.950% senior notes	640.9			—			January 15, 2025
1.375% senior notes	537.1			564.0			April 4, 2025
4.000% senior notes	742.9			742.1			June 1, 2025
4.400% senior notes	496.5			496.1			February 15, 2026
1.950% senior notes	538.6			566.0			May 22, 2026
3.375% senior notes	987.5			986.3			October 15, 2026
3.125% senior notes	397.6			397.3			January 15, 2027
3.55% senior notes	744.0			743.5			July 15, 2027
3.600% senior notes	692.4			691.9			January 15, 2028
3.950% senior notes	589.4			—			March 15, 2029
3.800% senior notes	1,631.3			—			August 15, 2029
Total American Tower Corporation debt	18,696.5			17,847.5

Series 2013-2A securities (5)	1,294.6			1,293.4			March 15, 2023
Series 2018-1A securities (5)	493.7			493.5			March 15, 2028
Series 2015-1 notes (6)	349.4			348.8			June 15, 2020
Series 2015-2 notes (7)	521.3			520.8			June 16, 2025
India indebtedness (8)	—			240.1			Various
India preference shares (9)	—			23.9			March 2, 2020
Shareholder loan (10)	—			59.9			December 31, 2019
Other subsidiary debt (11)	97.9			152.5			Various
Total American Tower subsidiary debt	2,756.9			3,132.9
Finance and capital lease obligations	30.2			179.5
Total	21,483.6			21,159.9
Less current portion of long-term obligations	(2,443.6		)	(2,754.8		)
Long-term obligations	$	19,040.0		$	18,405.1

_______________


(1)	Accrues interest at a variable rate.


(2)	Repaid in full on February 14, 2019 using proceeds from the 2019 Term Loan (as defined below) and cash on hand.


(3)	Repaid in full on the maturity date in February 2019 with borrowings from the 2013 Credit Facility and the 2014 Credit Facility (each as defined below).


(4)	Repaid in full on April 22, 2019 with borrowings from the 2014 Credit Facility and cash on hand.


(5)	Maturity date reflects the anticipated repayment date; final legal maturity is March 15, 2048.


(6)	Maturity date reflects the anticipated repayment date; final legal maturity is June 15, 2045.


(7)	Maturity date reflects the anticipated repayment date; final legal maturity is June 15, 2050.

(8)


(9)	Mandatorily redeemable preference shares (the “Preference Shares”) denominated in INR and classified as debt. The Preference Shares were redeemed on March 2, 2019.

(10)

(11)

Schedule of line of credit facilities



	Outstanding Principal Balance (in millions)		Undrawn letters of credit (in millions)		Maturity Date		Current margin over LIBOR (1)		Current commitment fee (2)
2013 Credit Facility	$	1,122.0	$	3.8	June 28, 2022	(3)	1.125	%	0.125	%
2014 Credit Facility	$	—	$	6.2	January 31, 2024	(3)	1.125	%	0.125	%
2013 Term Loan	$	1,000.0	N/A		January 31, 2024		1.125	%	N/A
2019 Term Loan	$	1,300.0	N/A		February 13, 2020		0.800	%	N/A

_______________

(1) LIBOR means the London Interbank Offered Rate.

(2) Fee on undrawn portion of each credit facility.

(3) Subject to two optional renewal periods.

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
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Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 942
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-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

STOCK-BASED COMPENSATION (Tables)

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Summary of stock-based compensation expenses

During the three and nine months ended September 30, 2019 and 2018, the Company recorded and capitalized the following stock-based compensation expense:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Stock-based compensation expense Property	$	0.4	$	0.8	$	1.4	$	2.0
Stock-based compensation expense Services	0.2		0.2		0.7		0.7
Stock-based compensation expense SG&A	22.9		42.8		85.8		108.6
Total stock-based compensation expense	$	23.5	$	43.8	$	87.9	$	111.3

Stock-based compensation expense capitalized as property and equipment	$	0.3	$	0.6	$	1.2	$	1.6

Summary of the company's option activity

The Company’s option activity for the nine months ended September 30, 2019 was as follows (shares disclosed in full amounts):



	Number of Options
Outstanding as of January 1, 2019	4,257,470
Granted	—
Exercised	(1,080,169	)
Forfeited	(7,211	)
Expired	—
Outstanding as of September 30, 2019	3,170,090

Summary of the company's restricted stock unit activity

The Company’s RSU and PSU activity for the nine months ended September 30, 2019 was as follows (shares disclosed in full amounts):



	RSUs		PSUs
Outstanding as of January 1, 2019 (1)	1,649,973		624,511
Granted (2)	542,744		114,823
Vested and Released (3)	(661,333	)	(338,680	)
Forfeited	(60,856	)	—
Outstanding as of September 30, 2019	1,470,528		400,654
Vested and deferred as of September 30, 2019 (4)	19,810		—

_______________

(1)


(2)	PSUs consist of the target number of shares issuable at the end of the three-year performance period for the 2019 PSUs, or 114,823 shares.


(3)	This includes 32,596 and 46,500 of previously vested and deferred RSUs and PSUs, respectively. PSUs consist of shares vested pursuant to the 2016 PSUs. There are no additional shares to be earned related to the 2016 PSUs.


(4)	Vested and deferred RSUs are related to deferred compensation for certain former employees.

EARNINGS PER COMMON SHARE (Tables)

9 Months Ended

Sep. 30, 2019

Earnings Per Share [Abstract]

Schedule of earnings per basic and diluted by common class

The following table sets forth basic and diluted net income per common share computational data (shares in thousands, except per share data):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Net income attributable to American Tower Corporation stockholders	$	498.6	$	366.9	$	1,325.1	$	958.8
Dividends on preferred stock	—		—		—		(9.4		)
Net income attributable to American Tower Corporation common stockholders	$	498.6	$	366.9	$	1,325.1	$	949.4
Basic weighted average common shares outstanding	442,763		440,889		442,110		439,191
Dilutive securities	3,066		3,232		3,242		3,277
Diluted weighted average common shares outstanding	445,829		444,121		445,352		442,468
Basic net income attributable to American Tower Corporation common stockholders per common share	$	1.13	$	0.83	$	3.00	$	2.16
Diluted net income attributable to American Tower Corporation common stockholders per common share	$	1.12	$	0.83	$	2.98	$	2.15

Schedule of antidilutive securities excluded from computation of earnings per share

The following shares were not included in the computation of diluted earnings per share because the effect would be anti-dilutive (in thousands, on a weighted average basis):



	Three Months Ended September 30,		Nine Months Ended September 30,
	2019	2018	2019	2018
Restricted stock units	—	3	1	2
Preferred stock	—	—	—	1,947

ACQUISITIONS (Tables)

9 Months Ended

Sep. 30, 2019

Business Combinations [Abstract]

Schedule of acquisition and merger related costs



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Acquisition and merger related expenses	$	5.8	$	0.9	$	11.6	$	6.8
Integration costs	$	1.6	$	9.8	$	7.8	$	15.0

Schedule of recognized identified assets acquired and liabilities assumed

The following table summarizes the allocations of the purchase prices for the fiscal year 2019 acquisitions based upon their estimated fair value at the date of acquisition:



	U.S. Acquisition			Other (1)
Current assets	$	4.0		$	7.9
Property and equipment	97.7			57.7
Intangible assets (2):
Tenant-related intangible assets	271.3			62.0
Network location intangible assets	110.9			27.0
Other intangible assets	—			0.8
Other non-current assets	55.5			7.8
Current liabilities	(2.4		)	(1.0		)
Deferred tax liability	—			—
Other non-current liabilities	(53.1		)	(12.7		)
Net assets acquired	483.9			149.5
Goodwill (3)	—			34.3
Fair value of net assets acquired	483.9			183.8
Debt assumed	—			—
Purchase price	$	483.9		$	183.8

_______________


(1)	Includes 106 sites in Peru held pursuant to long-term finance leases.


(2)	Tenant-related intangible assets and network location intangible assets are amortized on a straight-line basis over periods of up to 20 years.

(3)

The Company expects goodwill to be deductible for tax purposes.

Schedule of pro forma information



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Pro forma revenues	$	1,957.7	$	1,813.4	$	5,676.0	$	5,499.9
Pro forma net income attributable to American Tower Corporation common stockholders	$	497.7	$	363.3	$	1,321.9	$	937.8
Pro forma net income per common share amounts:
Basic net income attributable to American Tower Corporation common stockholders	$	1.12	$	0.82	$	2.99	$	2.14
Diluted net income attributable to American Tower Corporation common stockholders	$	1.12	$	0.82	$	2.97	$	2.12

BUSINESS SEGMENTS (Tables)

9 Months Ended

Sep. 30, 2019

Segment Reporting [Abstract]

Summarized financial information concerning the company's reportable segments



	Property								Total Property		Services		Other		Total
Three Months Ended September 30, 2019	U.S.		Asia		EMEA		Latin America		Total Property		Services		Other		Total
Segment revenues	$	1,095.9	$	312.5	$	181.5	$	331.7	$	1,921.6	$	32.0			$	1,953.6
Segment operating expenses (1)	207.5		177.9		58.6		103.6		547.6		11.7				559.3
Segment gross margin	888.4		134.6		122.9		228.1		1,374.0		20.3				1,394.3
Segment selling, general, administrative and development expense (1)	44.5		33.1		19.7		23.5		120.8		3.4				124.2
Segment operating profit	$	843.9	$	101.5	$	103.2	$	204.6	$	1,253.2	$	16.9			$	1,270.1
Stock-based compensation expense													$	23.5	23.5
Other selling, general, administrative and development expense													40.8		40.8
Depreciation, amortization and accretion													442.8		442.8
Other expense (2)													221.0		221.0
Income from continuing operations before income taxes															$	542.0
Total assets	$	22,653.2	$	5,324.9	$	3,626.6	$	7,129.2	$	38,733.9	$	55.8	$	517.5	$	39,307.2

_______________


(1)	Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $0.6 million and $22.9 million, respectively.


(2)	Primarily includes interest expense and $14.0 million in impairment charges.



	Property								Total Property		Services		Other		Total
Three Months Ended September 30, 2018	U.S.		Asia		EMEA		Latin America		Total Property		Services		Other		Total
Segment revenues	$	957.7	$	323.1	$	166.6	$	304.2	$	1,751.6	$	33.9			$	1,785.5
Segment operating expenses (1)	193.3		194.7		57.5		96.8		542.3		13.4				555.7
Interest income, TV Azteca, net	—		—		—		0.6		0.6		—				0.6
Segment gross margin	764.4		128.4		109.1		208.0		1,209.9		20.5				1,230.4
Segment selling, general, administrative and development expense (1)	37.9		13.5		16.2		20.7		88.3		6.3				94.6
Segment operating profit	$	726.5	$	114.9	$	92.9	$	187.3	$	1,121.6	$	14.2			$	1,135.8
Stock-based compensation expense													$	43.8	43.8
Other selling, general, administrative and development expense													40.5		40.5
Depreciation, amortization and accretion													448.9		448.9
Other expense (2)													212.8		212.8
Income from continuing operations before income taxes															$	389.8
Total assets	$	18,664.5	$	5,093.7	$	3,272.7	$	5,677.5	$	32,708.4	$	50.6	$	318.2	$	33,077.2

_______________


(1)	Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $1.0 million and $42.8 million, respectively.


(2)	Primarily includes interest expense and $1.8 million in impairment charges.



	Property								Total Property		Services		Other		Total
Nine Months Ended September 30, 2019	U.S.		Asia		EMEA		Latin America		Total Property		Services		Other		Total
Segment revenues	$	3,089.4	$	922.5	$	534.0	$	1,010.6	$	5,556.5	$	100.1			$	5,656.6
Segment operating expenses (1)	595.4		544.2		178.9		310.5		1,629.0		35.5				1,664.5
Segment gross margin	2,494.0		378.3		355.1		700.1		3,927.5		64.6				3,992.1
Segment selling, general, administrative and development expense (1)	128.4		77.4		58.1		75.0		338.9		8.8				347.7
Segment operating profit	$	2,365.6	$	300.9	$	297.0	$	625.1	$	3,588.6	$	55.8			$	3,644.4
Stock-based compensation expense													$	87.9	87.9
Other selling, general, administrative and development expense													117.3		117.3
Depreciation, amortization and accretion													1,328.6		1,328.6
Other expense (2)													663.1		663.1
Income from continuing operations before income taxes															$	1,447.5

_______________


(1)	Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $2.1 million and $85.8 million, respectively.


(2)	Primarily includes interest expense and $45.1 million in impairment charges.



	Property									Total Property			Services		Other		Total
Nine Months Ended September 30, 2018	U.S.		Asia		EMEA		Latin America			Total Property			Services		Other		Total
Segment revenues	$	2,846.1	$	904.0	$	507.5	$	953.8		$	5,211.4		$	96.8			$	5,308.2
Segment operating expenses (1)	578.4		532.7		175.1		309.5			1,595.7			38.5				1,634.2
Interest expense, TV Azteca, net	—		—		—		(0.1		)	(0.1		)	—				(0.1		)
Segment gross margin	2,267.7		371.3		332.4		644.2			3,615.6			58.3				3,673.9
Segment selling, general, administrative and development expense (1)	117.1		72.8		50.6		64.4			304.9			12.7				317.6
Segment operating profit	$	2,150.6	$	298.5	$	281.8	$	579.8		$	3,310.7		$	45.6			$	3,356.3
Stock-based compensation expense															$	111.3	111.3
Other selling, general, administrative and development expense															114.5		114.5
Depreciation, amortization and accretion															1,344.9		1,344.9
Other expense (2)															828.3		828.3
Income from continuing operations before income taxes																	$	957.3

_______________


(1)	Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $2.7 million and $108.6 million, respectively.

(2)

Primarily includes interest expense and $182.4 million in impairment charges.

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Details)	9 Months Ended
	Sep. 30, 2019 joint_venture
Concentration Risk [Line Items]
Number of joint ventures the Company has a controlling interest in (in joint ventures)	2
ATC Europe
Concentration Risk [Line Items]
Ownership interest (as a percent)	51.00%
Noncontrolling interest, ownership percentage by noncontrolling owners (as a percent)	49.00%
ATC, TIPL
Concentration Risk [Line Items]
Ownership interest (as a percent)	79.00%
Ghana
Concentration Risk [Line Items]
Number of joint ventures the Company has a controlling interest in (in joint ventures)	1
Uganda
Concentration Risk [Line Items]
Number of joint ventures the Company has a controlling interest in (in joint ventures)	1
Corporate Joint Venture \| Ghana
Concentration Risk [Line Items]
Ownership interest (as a percent)	51.00%
Noncontrolling interest, ownership percentage by noncontrolling owners (as a percent)	49.00%
Corporate Joint Venture \| SOUTH AFRICA
Concentration Risk [Line Items]
Ownership interest (as a percent)	81.00%
Noncontrolling interest, ownership percentage by noncontrolling owners (as a percent)	19.00%

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - CASH AND CASH EQUIVALENTS AND RESTRICTED CASH (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 1,352.6	$ 1,208.7	$ 1,026.5
Restricted cash	95.7	96.2	266.8
Total cash and cash equivalents and restricted cash	$ 1,448.3	$ 1,304.9	$ 1,293.3	$ 954.9

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - LEASES (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Distributions in excess of earnings	$ (1,130.1)		$ (1,199.5)
Lease liability	6,923.1
Right-of-use asset	$ 7,214.7
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Distributions in excess of earnings		$ 24.7
Lease liability		6,900.0
Right-of-use asset		$ 7,100.0

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - SUMMARY OF REVENUE DISAGGREGATED BY SOURCE AND GEOGRAPHY (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 137.3	$ 121.9	$ 402.8	$ 365.1
Property lease revenue	1,816.3	1,663.6	5,253.8	4,943.1
Total operating revenues	1,953.6	1,785.5	5,656.6	5,308.2
Non-lease property revenue
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	105.3	88.0	302.7	268.3
Services revenue
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	32.0	33.9	100.1	96.8
U.S.
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	98.7	96.3	286.4	287.1
Property lease revenue	1,029.2	895.3	2,903.1	2,655.8
Total operating revenues	1,127.9	991.6	3,189.5	2,942.9
U.S. \| Non-lease property revenue
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	66.7	62.4	186.3	190.3
U.S. \| Services revenue
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	32.0	33.9	100.1	96.8
Asia
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2.2	1.6	6.7	5.0
Property lease revenue	310.3	321.5	915.8	899.0
Total operating revenues	312.5	323.1	922.5	904.0
Asia \| Non-lease property revenue
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2.2	1.6	6.7	5.0
Asia \| Services revenue
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0.0	0.0	0.0	0.0
EMEA
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2.3	0.4	5.8	1.1
Property lease revenue	179.2	166.2	528.2	506.4
Total operating revenues	181.5	166.6	534.0	507.5
EMEA \| Non-lease property revenue
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2.3	0.4	5.8	1.1
EMEA \| Services revenue
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0.0	0.0	0.0	0.0
Latin America
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	34.1	23.6	103.9	71.9
Property lease revenue	297.6	280.6	906.7	881.9
Total operating revenues	331.7	304.2	1,010.6	953.8
Latin America \| Non-lease property revenue
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	34.1	23.6	103.9	71.9
Latin America \| Services revenue
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 0.0	$ 0.0	$ 0.0	$ 0.0

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - RECEIVABLES, CONTRACT ASSETS AND CONTRACT LIABILITIES FROM CONTRACTS WITH TENANTS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Schedule of Contract Assets And Liabilities From Contracts With Customers [Line Items]
Prepaids and other current assets	$ 472.0		$ 472.0		$ 621.2
Notes receivable and other non-current assets	248.9		248.9		962.6
Other non-current liabilities	870.9		870.9		1,265.1
Revenue recognized	15.7	$ 10.8	45.8	$ 33.3
Revenue recognized from change in contract assets	5.2	0.1	3.8	0.0
Other non-current liabilities
Schedule of Contract Assets And Liabilities From Contracts With Customers [Line Items]
Revenue recognized	0.1	0.2	0.3	0.4
Non-lease property revenue \| DAS
Schedule of Contract Assets And Liabilities From Contracts With Customers [Line Items]
Unearned revenue	56.1		56.1		55.0
Other non-current liabilities	301.6		301.6		313.6
Revenue recognized	14.8	$ 13.8	44.2	$ 41.2
Non-lease revenue
Schedule of Contract Assets And Liabilities From Contracts With Customers [Line Items]
Accounts receivable	94.0		94.0		92.6
Prepaids and other current assets	10.0		10.0		7.7
Notes receivable and other non-current assets	26.0		26.0		22.2
Unearned revenue	37.9		37.9		35.0
Other non-current liabilities	$ 68.8		$ 68.8		$ 54.1

PREPAID AND OTHER CURRENT ASSETS (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Unbilled receivables	$ 124.0	$ 126.1
Prepaid income tax	136.7	125.1
Value added tax and other consumption tax receivables	65.0	86.3
Prepaid assets	66.5	40.5
Prepaid operating ground leases	0.0	165.0
Other miscellaneous current assets	79.8	78.2
Prepaids and other current assets	$ 472.0	$ 621.2

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Towers	$ 13,044.9		$ 13,044.9		$ 12,777.9
Equipment	1,807.1		1,807.1		1,667.3
Buildings and improvements	636.2		636.2		628.5
Land and improvements	2,435.4		2,435.4		2,285.4
Construction-in-progress	378.7		378.7		358.1
Total	18,302.3		18,302.3		17,717.2
Less accumulated depreciation	(7,019.1)		(7,019.1)		(6,470.1)
Property and equipment, net	11,283.2		11,283.2		11,247.1
Depreciation	224.7	$ 221.0	$ 677.5	$ 666.9
Capital leased assets					4,369.5
Capital lease accumulated depreciation					$ 1,016.2
Towers \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)			20 years
Equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)			2 years
Equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)			20 years
Buildings and improvements \| Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)			3 years
Buildings and improvements \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)			32 years
Land and improvements \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)			20 years
Finance Lease Assets
Property, Plant and Equipment [Line Items]
Amortization of right-of-use asset	$ 42.4		$ 127.4

PROPERTY AND EQUIPMENT - FINANCE LEASES INCLUDED IN PROPERTY PLANT AND EQUIPMENT (Details) $ in Millions	Sep. 30, 2019 USD ($)
Property, Plant and Equipment [Line Items]
Land easements, not depreciable	$ 1,533.3
Towers
Property, Plant and Equipment [Line Items]
Property and equipment	2,706.9
Accumulated depreciation	(1,039.8)
Property and equipment, net	1,667.1
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property and equipment	171.4
Accumulated depreciation	(64.8)
Property and equipment, net	106.6
Land
Property, Plant and Equipment [Line Items]
Property and equipment	152.1
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment	45.0
Accumulated depreciation	(11.9)
Property and equipment, net	$ 33.1

LEASES - NARRATIVE (Details)	3 Months Ended		9 Months Ended
LEASES - NARRATIVE (Details)	Sep. 30, 2019 USD ($) tenant	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) tenant renewal_option	Sep. 30, 2018 USD ($)	Aug. 30, 2019 USD ($)
Lessor, Lease, Description [Line Items]
Number of tenants on site (more than) \| tenant	1		1
Lessor, Operating Lease, Payments to be Received	$ 46,265,400,000		$ 46,265,400,000
Lessee, renewal term \| renewal_option			1
Asset impairments	14,000,000.0	$ 1,800,000	$ 45,100,000	$ 182,400,000
Interest expense on finance lease liabilities	$ 400,000		1,100,000
Lease Agreements
Lessor, Lease, Description [Line Items]
Asset impairments			$ 0
Minimum
Lessor, Lease, Description [Line Items]
Lessor, terms of contract	5 years		5 years
Lessee, lease term	5 years		5 years
Maximum
Lessor, Lease, Description [Line Items]
Lessor, terms of contract	10 years		10 years
Lessee, lease term	10 years		10 years
Maximum \| Communication Sites
Lessor, Lease, Description [Line Items]
Estimated useful life			20 years
AT&T Transaction
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Payments to be Received					$ 13,700,000,000

LEASES - MATURITIES OF MINIMUM RENTAL RECEIPTS EXPECTED UNDER NON-CANCELLABLE OPERATING LEASES (Details) $ in Millions	Sep. 30, 2019 USD ($)
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2019	$ 1,394.7
2020	5,645.9
2021	5,442.0
2022	4,846.6
2023	4,710.8
Thereafter	24,225.4
Total	$ 46,265.4

LEASES - SCHEDULE OF FUTURE MINIMUM RENTAL RECEIPTS EXPECTED BEFORE TOPIC 842 (Details) $ in Millions	Dec. 31, 2018 USD ($)
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
2019	$ 5,251.2
2020	5,062.2
2021	4,676.1
2022	3,754.6
2023	3,457.3
Thereafter	12,641.1
Total	$ 34,842.5

LEASES - SCHEDULE OF INFORMATION ABOUT OTHER LEASE RELATED BALANCES (Details) $ in Millions	Sep. 30, 2019 USD ($)
Operating leases:
Right-of-use asset	$ 7,214.7
Current portion of lease liability	475.1
Lease liability	6,448.0
Total operating lease liability	6,923.1
Finance leases:
Current portion of lease liability	7.1
Lease liability	23.1
Total finance lease liability	$ 30.2

LEASES - SCHEDULE OF WEIGHTED AVERAGE LEASE TERMS AND DISCOUNT RATES BY SEGMENT (Details)	Sep. 30, 2019
Operating leases:
Weighted-average remaining lease term (years)	13 years 3 months 18 days
Weighted-average incremental borrowing rate	6.30%
Finance leases:
Weighted-average remaining lease term (years)	15 years
Weighted-average incremental borrowing rate	6.20%

LEASES - SUPPLEMENTAL CASH FLOW INFOMATION (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ (701.9)
Operating cash flows from finance leases	(1.1)
Financing cash flows from finance leases	(16.4)
Non-cash items:
New operating leases	224.8
Operating lease modifications and reassessments	$ 338.9

LEASES - MATURITIES OF OPERATING AND FINANCE LEASE LIABILITIES (Details) $ in Millions	Sep. 30, 2019 USD ($)
Operating Lease
Remainder of 2019	$ 217.4
2020	876.0
2021	860.4
2022	822.4
2023	785.4
Thereafter	6,735.8
Total lease payments	10,297.4
Less amounts representing interest	(3,374.3)
Total operating lease liability	6,923.1
Less current portion of lease liability	(475.1)
Non-current lease liability	6,448.0
Finance Lease
Remainder of 2019	2.8
2020	7.6
2021	4.9
2022	4.0
2023	2.6
Thereafter	45.5
Total lease payments	67.4
Less amounts representing interest	(37.2)
Total finance lease liability	30.2
Less current portion of lease liability	(7.1)
Non-current lease liability	$ 23.1

LEASES - MATURITIES OF OPERATING AND CAPITAL LEASES BEFORE ADOPTION OF 842 (Details) $ in Millions	Dec. 31, 2018 USD ($)
Operating Leases Before Adoption of 842 [Abstract]
2019	$ 926.0
2020	904.2
2021	879.8
2022	834.2
2023	792.6
Thereafter	6,173.1
Total	10,509.9
Capital Leases Before Adoption of 842
2019	40.7
2020	32.7
2021	27.8
2022	23.7
2023	19.2
Thereafter	117.5
Total	261.6
Less amounts representing interest	(82.1)
Present value of capital lease obligations	$ 179.5

GOODWILL AND OTHER INTANGIBLE ASSETS - CHANGES IN THE CARRYING VALUE OF GOODWILL (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 5,501.9
Additions and adjustments	33.5
Effect of foreign currency translation	(54.0)
Goodwill, ending balance	5,481.4
Other Acquisitions 2019
Goodwill [Roll Forward]
Goodwill, ending balance	34.3
Property \| U.S.
Goodwill [Roll Forward]
Goodwill, beginning balance	3,382.5
Additions and adjustments	33.5
Effect of foreign currency translation	0.0
Goodwill, ending balance	3,416.0
Goodwill, purchase accounting adjustments	0.8
Property \| U.S. \| Other Acquisitions 2019
Goodwill [Roll Forward]
Additions and adjustments	34.3
Property \| Asia
Goodwill [Roll Forward]
Goodwill, beginning balance	1,045.5
Additions and adjustments	0.0
Effect of foreign currency translation	(16.3)
Goodwill, ending balance	1,029.2
Property \| EMEA
Goodwill [Roll Forward]
Goodwill, beginning balance	381.3
Additions and adjustments	0.0
Effect of foreign currency translation	(16.8)
Goodwill, ending balance	364.5
Property \| Latin America
Goodwill [Roll Forward]
Goodwill, beginning balance	690.6
Additions and adjustments	0.0
Effect of foreign currency translation	(20.9)
Goodwill, ending balance	669.7
Services
Goodwill [Roll Forward]
Goodwill, beginning balance	2.0
Additions and adjustments	0.0
Effect of foreign currency translation	0.0
Goodwill, ending balance	$ 2.0

GOODWILL AND OTHER INTANGIBLE ASSETS - INTANGIBLE ASSETS SUBJECT TO AMORTIZATION (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 16,295.8	$ 16,040.9
Accumulated Amortization	(5,400.0)	(4,866.6)
Net Book Value	10,895.8	11,174.3
Network location intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	4,832.7	4,780.3
Accumulated Amortization	(1,863.2)	(1,704.9)
Net Book Value	$ 2,969.5	3,075.4
Network location intangible assets \| Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives (years)	20 years
Acquired tenant-related intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 11,359.2	11,156.5
Accumulated Amortization	(3,517.3)	(3,147.2)
Net Book Value	$ 7,841.9	8,009.3
Acquired tenant-related intangibles \| Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives (years)	15 years
Acquired tenant-related intangibles \| Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives (years)	20 years
Acquired licenses and other intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 103.9	104.1
Accumulated Amortization	(19.5)	(14.5)
Net Book Value	$ 84.4	$ 89.6
Acquired licenses and other intangibles \| Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives (years)	3 years
Acquired licenses and other intangibles \| Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives (years)	20 years

GOODWILL AND OTHER INTANGIBLE ASSETS - EXPECTED FUTURE AMORTIZATION EXPENSE (Details) $ in Millions	Sep. 30, 2019 USD ($)
Fiscal Year
Remainder of 2019	$ 199.0
2020	777.8
2021	761.7
2022	757.7
2023	753.8
2024	$ 750.8

ACCRUED EXPENSES (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued property and real estate taxes	$ 195.1	$ 169.7
Accrued pass-through costs	74.4	71.2
Amounts payable to tenants	65.8	93.5
Accrued rent	75.3	61.4
Payroll and related withholdings	81.4	90.4
Accrued construction costs	30.0	41.5
Accrued income tax payable	34.1	57.9
Accrued pass-through taxes	5.2	2.2
Other accrued expenses	295.4	360.5
Total accrued expenses	$ 856.7	$ 948.3

LONG-TERM OBLIGATIONS - SCHEDULE OF LONG-TERM OBLIGATIONS (Details) GH₵ in Millions, $ in Millions			9 Months Ended
	Jun. 14, 2019 USD ($)	Jun. 14, 2019 GHS (GH₵)	Sep. 30, 2019 USD ($)	Jun. 13, 2019	Apr. 22, 2019	Mar. 15, 2019	Feb. 15, 2019	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Finance and capital lease obligations			$ 30.2
Finance and capital lease obligations								$ 179.5
Total			21,483.6					21,159.9
Less current portion of long-term obligations			(2,443.6)					(2,754.8)
Long-term obligations			19,040.0					18,405.1
American Tower Corporation
Debt Instrument [Line Items]
Long-term debt			18,696.5					17,847.5
American Tower subsidiary
Debt Instrument [Line Items]
Long-term debt			2,756.9					3,132.9
2018 Term Loan \| Unsecured debt
Debt Instrument [Line Items]
Long-term debt			0.0					1,499.8
Repayment of loans			1,500.0
2019 Term Loan \| Unsecured debt
Debt Instrument [Line Items]
Long-term debt			1,299.8					0.0
2013 Credit Facility \| Credit Facility
Debt Instrument [Line Items]
Line of credit			1,122.0					1,875.0
2013 Term Loan \| Unsecured debt
Debt Instrument [Line Items]
Long-term debt			995.5					994.8
2014 Credit Facility \| Credit Facility
Debt Instrument [Line Items]
Line of credit			0.0					$ 0.0
3.40% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)							3.40%	3.40%
Long-term debt			$ 0.0					$ 1,000.0
2.800% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			2.80%
Long-term debt			$ 749.0					$ 747.8
5.050% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)					5.05%			5.05%
Long-term debt			$ 0.0					$ 698.7
3.300% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.30%
Long-term debt			$ 748.2					747.2
3.450% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.45%
Long-term debt			$ 647.3					646.3
5.900% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			5.90%
Long-term debt			$ 498.8					498.4
2.250% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			2.25%
Long-term debt			$ 592.0					572.7
4.70% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			4.70%
Long-term debt			$ 698.0					697.4
3.50% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.50%
Long-term debt			$ 993.8					992.6
3.000% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.00%
Long-term debt			$ 708.0					687.5
5.00% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			5.00%
Long-term debt			$ 1,001.8					1,002.1
3.375% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.375%
Long-term debt			$ 644.1					0.0
2.950% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			2.95%	2.95%
Long-term debt			$ 640.9					0.0
1.375% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			1.375%
Long-term debt			$ 537.1					564.0
4.000% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			4.00%
Long-term debt			$ 742.9					742.1
4.400% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			4.40%
Long-term debt			$ 496.5					496.1
1.950% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			1.95%
Long-term debt			$ 538.6					566.0
3.375% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.375%			3.375%
Long-term debt			$ 987.5					986.3
3.125% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.125%
Long-term debt			$ 397.6					397.3
3.55% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.55%
Long-term debt			$ 744.0					743.5
3.600% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.60%
Long-term debt			$ 692.4					691.9
3.950% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.95%			3.95%
Long-term debt			$ 589.4					0.0
3.800% senior notes \| Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.80%	3.80%
Long-term debt			$ 1,631.3					0.0
Series 2013-2A securities \| Secured debt \| Series 2013-2A securities
Debt Instrument [Line Items]
Long-term debt			1,294.6					1,293.4
Series 2018-1A securities \| Secured debt \| Series 2018-1A securities
Debt Instrument [Line Items]
Long-term debt			493.7					493.5
Series 2015-1 notes \| Secured debt
Debt Instrument [Line Items]
Long-term debt			349.4					348.8
Series 2015-2 notes \| Secured debt
Debt Instrument [Line Items]
Long-term debt			521.3					520.8
India indebtedness \| Unsecured debt
Debt Instrument [Line Items]
Long-term debt			0.0					240.1
India preference shares \| Mandatorily redeemable preferred stock
Debt Instrument [Line Items]
Long-term debt			0.0					23.9
Shareholder loans \| Unsecured debt
Debt Instrument [Line Items]
Long-term debt			0.0					59.9
Repayment of loans	$ 56.8	GH₵ 294.4
Other subsidiary debt \| Unsecured debt
Debt Instrument [Line Items]
Long-term debt			$ 97.9					$ 152.5
Debt repayment period			3 years

LONG-TERM OBLIGATIONS - NARRATIVE (Details)					3 Months Ended		9 Months Ended
LONG-TERM OBLIGATIONS - NARRATIVE (Details)	Jun. 13, 2019 USD ($)	Apr. 22, 2019 USD ($)	Mar. 15, 2019 EUR (€)	Feb. 15, 2019 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Current portion of long-term obligations					$ 2,443,600,000		$ 2,443,600,000		$ 2,754,800,000
Loss on retirement of long-term obligations					0	$ 0	22,200,000	$ 0
Proceeds from issuance of debt							1,300,000,000.0	1,500,000,000.0
Borrowings under credit facilities							3,330,000,000.0	$ 2,913,300,000
2013 Credit Facility \| Credit Facility
Debt Instrument [Line Items]
Borrowings under credit facilities							1,700,000,000
Repayment of indebtedness under credit facility							2,500,000,000
2014 Credit Facility \| Credit Facility
Debt Instrument [Line Items]
Borrowings under credit facilities							1,600,000,000
Repayment of indebtedness under credit facility							1,600,000,000
Unsecured debt \| 2019 Term Loan
Debt Instrument [Line Items]
Current portion of long-term obligations					$ 1,300,000,000		1,300,000,000
Unsecured debt \| 2018 Term Loan
Debt Instrument [Line Items]
Repayment of loans							$ 1,500,000,000
Senior notes
Debt Instrument [Line Items]
Debt redemption price rate (as a percent)	100.00%
Change in control repurchase price as percentage of principal			101.00%
Maximum adjusted EBITDA					3.5		3.5
Senior notes \| 2.800% senior notes
Debt Instrument [Line Items]
Current portion of long-term obligations					$ 750,000,000.0		$ 750,000,000.0
Long-term debt, stated interest rate (as a percent)					2.80%		2.80%
Senior notes \| 3.40% senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)				3.40%					3.40%
Repayments of senior debt				$ 1,000,000,000.0
Senior notes \| 5.050% senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)		5.05%							5.05%
Debt redeemed aggregate principal amount		$ 700,000,000.0
Debt redemption price rate (as a percent)		103.005%
Debt redeemed aggregate redemption price		$ 726,000,000.0
Accrued and unpaid interest		5,000,000.0
Loss on retirement of long-term obligations		22,100,000
Prepayment consideration		$ 21,000,000.0
Senior notes \| 3.375% senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.375%		3.375%		3.375%
Senior note public offering, amount \| €			€ 650,000,000.0
Proceeds from issuance of debt	$ 2,269,000,000.0		€ 1,231,000,000.0
Senior notes \| 3.950% senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)			3.95%		3.95%		3.95%
Senior note public offering, amount \| €			€ 600,000,000.0
Debt, interest accrual period			360 days
Senior notes \| 2.950% senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	2.95%				2.95%		2.95%
Senior note public offering, amount	$ 650,000,000.0
Debt, interest accrual period	360 days
Senior notes \| 3.800% senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.80%				3.80%		3.80%
Senior note public offering, amount	$ 1,650,000,000
Secured debt \| Series 2015-1 notes
Debt Instrument [Line Items]
Current portion of long-term obligations					$ 350,000,000.0		$ 350,000,000.0

LONG-TERM OBLIGATIONS - SCHEDULE OF LINES OF CREDIT (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($) renewal_period
2013 Credit Facility \| Credit Facility
Line of Credit Facility [Line Items]
Outstanding Principal Balance	$ 1,122.0
Undrawn letters of credit	$ 3.8
Current commitment fee (as a percent)	0.125%
2013 Credit Facility \| Credit Facility \| LIBOR
Line of Credit Facility [Line Items]
Current margin over LIBOR (as a percent)	1.125%
2014 Credit Facility \| Credit Facility
Line of Credit Facility [Line Items]
Outstanding Principal Balance	$ 0.0
Undrawn letters of credit	$ 6.2
Current commitment fee (as a percent)	0.125%
Optional renewal periods \| renewal_period	2
2014 Credit Facility \| Credit Facility \| LIBOR
Line of Credit Facility [Line Items]
Current margin over LIBOR (as a percent)	1.125%
2013 Term Loan \| Unsecured debt
Line of Credit Facility [Line Items]
Outstanding Principal Balance	$ 1,000.0
2013 Term Loan \| Unsecured debt \| LIBOR
Line of Credit Facility [Line Items]
Current margin over LIBOR (as a percent)	1.125%
2019 Term Loan \| Unsecured debt
Line of Credit Facility [Line Items]
Outstanding Principal Balance	$ 1,300.0
2019 Term Loan \| Unsecured debt \| LIBOR
Line of Credit Facility [Line Items]
Current margin over LIBOR (as a percent)	0.80%

FAIR VALUE MEASUREMENTS - ASSETS AND LIABILITIES MEASURED AT FAIR VALUE ON A RECURRING BASIS (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Level 1
Assets:
Embedded derivative in lease agreement	$ 0.0	$ 0.0
Liabilities:
Acquisition-related contingent consideration	0.0	0.0
Redeemable noncontrolling interests	0.0	0.0
Level 1 \| Interest rate swap agreements
Assets:
Interest rate swap agreements	0.0	0.0
Liabilities:
Interest rate swap agreements	0.0	0.0
Fair value of debt related to interest swap agreements	7.0	(31.3)
Level 2
Assets:
Embedded derivative in lease agreement	0.0	0.0
Liabilities:
Acquisition-related contingent consideration	0.0	0.0
Redeemable noncontrolling interests	0.0	0.0
Level 2 \| Interest rate swap agreements
Assets:
Interest rate swap agreements	12.7	0.0
Liabilities:
Interest rate swap agreements	7.3	33.8
Fair value of debt related to interest swap agreements	0.0	0.0
Level 3
Assets:
Embedded derivative in lease agreement	10.9	11.5
Liabilities:
Acquisition-related contingent consideration	0.8	0.9
Redeemable noncontrolling interests	574.8	1,004.8
Level 3 \| Interest rate swap agreements
Assets:
Interest rate swap agreements	0.0	0.0
Liabilities:
Interest rate swap agreements	0.0	0.0
Fair value of debt related to interest swap agreements	$ 0.0	$ 0.0

FAIR VALUE MEASUREMENTS - NARRATIVE (Details) - USD ($)	3 Months Ended	9 Months Ended
FAIR VALUE MEASUREMENTS - NARRATIVE (Details) - USD ($)	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business combination, contingent consideration arrangements, range of outcomes, value, low		$ 0
Business combination, contingent consideration arrangements, range of outcomes, value, high		800,000
Asset impairments	$ 1,800,000	45,100,000	$ 182,400,000
Long-term obligations		21,483,600,000		$ 21,159,900,000
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value		22,400,000,000		21,100,000,000
Estimate of Fair Value Measurement \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value		16,100,000,000		13,400,000,000
Estimate of Fair Value Measurement \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value		$ 6,300,000,000		$ 7,700,000,000

INCOME TAXES - NARRATIVE (Details) - USD ($)	3 Months Ended	9 Months Ended
INCOME TAXES - NARRATIVE (Details) - USD ($)	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact the ETR	$ 93,300,000	$ 93,300,000	$ 93,700,000
Unrecognized tax benefits, increase resulting from current period tax positions	1,400,000	4,400,000
Unrecognized tax benefits, from foreign currency fluctuations	(3,700,000)	(2,700,000)
Unrecognized tax benefits, income tax penalties and interest accrued	22,700,000	22,700,000	$ 19,100,000
Minimum
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefits is reasonably possible	0	0
Maximum
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefits is reasonably possible	$ 27,500,000	$ 27,500,000

STOCK-BASED COMPENSATION - NARRATIVE (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended			12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ESPP, discount rate (as a percent)			15.00%
Total unrecognized compensation expense	$ 1.4		$ 1.4
Stock-based compensation expense	23.5	$ 43.8	$ 87.9	$ 111.3
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected recognition of stock award compensation expense weighted average period ( less than one year for stock options)			2 years
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years			3 years	3 years
Total unrecognized compensation expense	15.0		$ 15.0
Expected recognition of stock award compensation expense weighted average period ( less than one year for stock options)			2 years
Performance grant, shares granted (in shares)			114,823	131,311	154,520
Stock-based compensation expense	$ 4.6		$ 18.1
Performance Shares \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of potential target shares			0.00%
Performance Shares \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of potential target shares			200.00%
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected recognition of stock award compensation expense weighted average period ( less than one year for stock options)			1 year
2007 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issuable under stock incentive plan (in shares)	7,000,000.0		7,000,000.0
2007 Plan \| RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Total unrecognized compensation expense	$ 137.8		$ 137.8
2007 Plan \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
2007 Plan \| Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period			10 years

STOCK-BASED COMPENSATION - SUMMARY OF THE COMPANY'S OPTION ACTIVITY (Details) - Employee Stock Option	9 Months Ended
	Sep. 30, 2019 shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding as of January 1, 2019 (in shares)	4,257,470
Granted (in shares)	0
Exercised (in shares)	(1,080,169)
Forfeited (in shares)	(7,211)
Expired (in shares)	0
Outstanding as of June 30, 2019 (in shares)	3,170,090

STOCK-BASED COMPENSATION - SUMMARY OF THE COMPANY'S RESTRICTED STOCK UNIT ACTIVITY (Details) - shares	9 Months Ended			12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Shares issued based upon achievement against performance metrics (in shares)				338,680
RSUs
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Outstanding as of January 1, 2019 (in shares)	1,649,973
Granted (in shares)	542,744
Vested (in shares)	(661,333)
Forfeited (in shares)	(60,856)
Outstanding as of June 30, 2019 (in shares)	1,470,528			1,649,973
Vested and deferred as of June 30, 2019 (in shares)	19,810			32,596
PSUs
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Outstanding as of January 1, 2019 (in shares)	624,511
Granted (in shares)	114,823
Vested (in shares)	(338,680)
Forfeited (in shares)	0
Outstanding as of June 30, 2019 (in shares)	400,654			624,511
Vested and deferred as of June 30, 2019 (in shares)	0			46,500
Vesting period	3 years			3 years	3 years
Three year performance grant, shares granted (in shares)	114,823	131,311	154,520

REDEEMABLE NONCONTROLLING INTERESTS - NARRATIVE (Details) ₨ / shares in Units, $ in Millions, ₨ in Billions	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2019 USD ($)	Mar. 31, 2020	Dec. 31, 2018	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 INR (₨) ₨ / shares	Apr. 30, 2019 INR (₨)	Apr. 21, 2016
Noncontrolling Interest [Line Items]
Adjustment to noncontrolling interest redemption value				$ (2.2)	$ 28.6
Temporary equity, redemption price per share (in dollars per share) \| ₨ / shares						₨ 216
Redemption consideration value	$ 350.1			$ 425.7		₨ 29.4	₨ 24.8
Tata Teleservices Limited
Noncontrolling Interest [Line Items]
Percentage of ownership before transaction	100.00%			50.00%
Percentage of ownership after transaction			63.00%	79.00%
IDFC
Noncontrolling Interest [Line Items]
Percentage of ownership before transaction				100.00%
Viom Transaction
Noncontrolling Interest [Line Items]
Percentage of interests acquired								51.00%
Adjustment to noncontrolling interest redemption value				$ (2.2)	$ 28.6
Noncontrolling interest, ownership percentage by noncontrolling owners (as a percent)			37.00%	21.00%		21.00%
Scenario, Forecast \| Tata Teleservices Limited
Noncontrolling Interest [Line Items]
Percentage of ownership after transaction		92.00%

REDEEMABLE NONCONTROLLING INTERESTS - CHANGE IN REDEEMABLE NONCONTROLLING INTEREST (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Increase (Decrease) in Temporary Equity [Roll Forward]
Balance as of January 1,	$ 1,004.8	$ 1,126.2
Net income (loss) attributable to noncontrolling interests	2.2	(42.4)
Adjustment to noncontrolling interest redemption value	(2.2)	28.6
Adjustment to noncontrolling interest due to merger	0.0	(20.5)
Purchase of redeemable noncontrolling interest	425.7	0.0
Foreign currency translation adjustment attributable to noncontrolling interests	(4.3)	(129.5)
Balance as of June 30,	574.8	954.8
Merger
Increase (Decrease) in Temporary Equity [Roll Forward]
Adjustment to noncontrolling interest due to merger	$ 0.0	$ (28.1)

EQUITY - NARRATIVE (Details) - USD ($)	9 Months Ended
EQUITY - NARRATIVE (Details) - USD ($)	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2011
Class of Stock [Line Items]
Proceeds from stock options and employee stock purchase plan	$ 92,700,000	$ 54,100,000
Treasury stock activity (in shares)	0
Shares repurchased (in shares)	10,557,000		10,557,000
Shares repurchased	$ 1,206,800,000		$ 1,206,800,000
Accrued dividend RSU	12,300,000
Paid dividend RSU	$ 6,900,000	$ 4,200,000
2011 Buyback
Class of Stock [Line Items]
Stock repurchase program, authorized amount					$ 1,500,000,000
Shares repurchased (in shares)	14,003,543
Shares repurchased	$ 1,400,000,000
2017 Buyback
Class of Stock [Line Items]
Stock repurchase program, authorized amount				$ 2,000,000,000.0

EQUITY - DISTRIBUTIONS (Details) - USD ($) $ / shares in Units, $ in Millions																		9 Months Ended
	Oct. 03, 2019	Sep. 13, 2019	Jul. 12, 2019	May 22, 2019	Apr. 26, 2019	Mar. 07, 2019	Jan. 14, 2019	Dec. 05, 2018	Oct. 17, 2018	Sep. 06, 2018	Jul. 13, 2018	May 24, 2018	Apr. 27, 2018	Mar. 08, 2018	Jan. 22, 2018	Jan. 16, 2018	Dec. 07, 2017	Sep. 30, 2019	Sep. 30, 2018
Dividends Payable [Line Items]
Aggregate Payment Amount on common stock																		$ 1,182.2	$ 975.1
Aggregate Payment Amount on preferred stock																		$ 0.0	$ 18.9
Common Stock
Dividends Payable [Line Items]
Distribution per share, common stock (in dollars per share)		$ 0.95		$ 0.92		$ 0.90		$ 0.84		$ 0.79		$ 0.77		$ 0.75			$ 0.70
Aggregate Payment Amount on common stock			$ 407.0		$ 397.8		$ 370.5		$ 348.3		$ 339.8		$ 331.2			$ 300.2
Common Stock \| Subsequent Event
Dividends Payable [Line Items]
Aggregate Payment Amount on common stock	$ 420.7
Preferred Stock - Series B
Dividends Payable [Line Items]
Distribution per share, preferred stock (in dollars per share)															$ 13.75
Aggregate Payment Amount on preferred stock															$ 18.9

EARNINGS PER COMMON SHARE - SCHEDULE OF EARNINGS PER BASIC AND DILUTED BY COMMON CLASS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net income attributable to American Tower Corporation stockholders	$ 498.6	$ 366.9	$ 1,325.1	$ 958.8
Dividends on preferred stock	0.0	0.0	0.0	(9.4)
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION COMMON STOCKHOLDERS	$ 498.6	$ 366.9	$ 1,325.1	$ 949.4
Basic weighted average common shares outstanding (in shares)	442,763	440,889	442,110	439,191
Dilutive securities (in shares)	3,066	3,232	3,242	3,277
Diluted weighted average common shares outstanding (in shares)	445,829	444,121	445,352	442,468
Basic net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 1.13	$ 0.83	$ 3.00	$ 2.16
Diluted net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 1.12	$ 0.83	$ 2.98	$ 2.15

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

COMMITMENTS AND CONTINGENCIES - NARRATIVE (Details) ₨ in Millions, $ in Millions					1 Months Ended	9 Months Ended
	Aug. 30, 2019 USD ($) communications_site	Dec. 05, 2016 USD ($)	Dec. 05, 2016 INR (₨)	Mar. 27, 2015 USD ($) communications_site renewal_period	Dec. 31, 2000 tower	Sep. 30, 2019 USD ($) tower renewal_period	Dec. 31, 2016 tower
INDIA
Loss Contingencies [Line Items]
Foreign income tax assessment		$ 69.8	₨ 4,750
ALLTEL Transaction
Loss Contingencies [Line Items]
Aggregate purchase price \| $	$ 43.0
ALLTEL Transaction \| Towers
Loss Contingencies [Line Items]
Number of communications sites acquired (in number of towers) \| communications_site	243
Verizon Transaction
Loss Contingencies [Line Items]
Capital leased assets, number of units (in number of communication sites) \| communications_site				11,250
Right to lease, weighted average term				28 years
Aggregate purchase option price for towers \| $				$ 5,000.0
Customer lease, initial term				10 years
Successive terms to renew lease (in numbers of terms) \| renewal_period				8
Renewal term				5 years
AT&T Transaction
Loss Contingencies [Line Items]
Capital leased assets, number of units (in number of communication sites)						2,270
Aggregate purchase option price for towers \| $						$ 955.7
Successive terms to renew lease (in numbers of terms) \| renewal_period						4
Renewal term						5 years
Operating lease, term of contract						27 years
Number of sites acquired life to date						154
Purchase price accretion rate (per year)						10.00%
ALLTEL Transaction
Loss Contingencies [Line Items]
Capital leased assets, number of units (in number of communication sites)					1,800
Average lease term (in years)					15 years
Number of communications sites acquired (in number of towers)							1,523
Number of remaining towers							243

ACQUISITIONS - NARRATIVE (Details) $ in Millions			3 Months Ended	9 Months Ended
ACQUISITIONS - NARRATIVE (Details) $ in Millions	Aug. 30, 2019 USD ($) communications_site	May 30, 2019 USD ($) markets communications_site	Sep. 30, 2019 USD ($) communications_site	Sep. 30, 2019 USD ($) communications_site
Business Acquisition [Line Items]
Payment received related to acquisition in France				$ 13.1
Estimated aggregate impact of acquisitions completed, revenue			$ 5.3	7.9
Estimated aggregate impact of acquisitions completed, gross margin			$ 3.9	5.7
African Markets
Business Acquisition [Line Items]
Number of markets in which entity operates \| markets		5
Eaton Towers Holding Limited
Business Acquisition [Line Items]
Percentage of interests acquired		100.00%
Eaton Towers Holding Limited \| Communication Sites
Business Acquisition [Line Items]
Number of communications sites acquired (in number of towers) \| communications_site		5,500
Purchase price		$ 1,850.0
U.S. Acquisition
Business Acquisition [Line Items]
Number of communications sites acquired (in number of towers) \| communications_site	400
Aggregate purchase price	$ 483.9
Other Acquisitions 2019
Business Acquisition [Line Items]
Aggregate purchase price				$ 183.8
Other Acquisitions 2019 \| Communication Sites
Business Acquisition [Line Items]
Number of communications sites acquired (in number of towers) \| communications_site			582	582
ALLTEL Transaction
Business Acquisition [Line Items]
Aggregate purchase price	$ 43.0
ALLTEL Transaction \| Towers
Business Acquisition [Line Items]
Number of communications sites acquired (in number of towers) \| communications_site	243

ACQUISITIONS - SUMMARY OF ALLOCATION OF THE PURCHASE PRICE (Details) $ in Millions		9 Months Ended
	Aug. 30, 2019 USD ($) communications_site	Sep. 30, 2019 USD ($) site	Dec. 31, 2018 USD ($)
Asset Acquisition:
Goodwill		$ 5,481.4	$ 5,501.9
Tenant-related intangible assets \| Maximum
Asset Acquisition:
Estimated useful lives (in years)		20 years
Network location intangible assets \| Maximum
Asset Acquisition:
Estimated useful lives (in years)		20 years
U.S. Acquisition
Asset Acquisition:
Current assets	$ 4.0
Property and equipment	97.7
Other non-current assets	55.5
Current liabilities	(2.4)
Deferred tax liability	0.0
Other non-current liabilities	(53.1)
Net assets acquired	483.9
Goodwill	0.0
Fair value of net assets acquired	483.9
Debt assumed	0.0
Purchase price	$ 483.9
Number of sites acquired \| communications_site	400
U.S. Acquisition \| Tenant-related intangible assets
Asset Acquisition:
Intangible assets	$ 271.3
U.S. Acquisition \| Network location intangible assets
Asset Acquisition:
Intangible assets	110.9
U.S. Acquisition \| Other intangible assets
Asset Acquisition:
Intangible assets	$ 0.0
Other Acquisitions 2019
Asset Acquisition:
Current assets		$ 7.9
Property and equipment		57.7
Other non-current assets		7.8
Current liabilities		(1.0)
Deferred tax liability		0.0
Other non-current liabilities		(12.7)
Net assets acquired		149.5
Goodwill		34.3
Fair value of net assets acquired		183.8
Debt assumed		0.0
Purchase price		$ 183.8
Other Acquisitions 2019 \| Peru
Asset Acquisition:
Number of sites acquired \| site		106
Other Acquisitions 2019 \| Tenant-related intangible assets
Asset Acquisition:
Intangible assets		$ 62.0
Other Acquisitions 2019 \| Tenant-related intangible assets \| Maximum
Asset Acquisition:
Estimated useful lives (in years)		20 years
Other Acquisitions 2019 \| Network location intangible assets
Asset Acquisition:
Intangible assets		$ 27.0
Other Acquisitions 2019 \| Network location intangible assets \| Maximum
Asset Acquisition:
Estimated useful lives (in years)		20 years
Other Acquisitions 2019 \| Other intangible assets
Asset Acquisition:
Intangible assets		$ 0.8

ACQUISITIONS - PRO FORMA INFORMATION (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Business Combinations [Abstract]
Pro forma revenues	$ 1,957.7	$ 1,813.4	$ 5,676.0	$ 5,499.9
Pro forma net income attributable to American Tower Corporation common stockholders	$ 497.7	$ 363.3	$ 1,321.9	$ 937.8
Pro forma net income per common share amounts:
Basic net income attributable to American Tower Corporation common stockholders (in dollars per share)	$ 1.12	$ 0.82	$ 2.99	$ 2.14
Diluted net income attributable to American Tower Corporation common stockholders (in dollars per share)	$ 1.12	$ 0.82	$ 2.97	$ 2.12

BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 1,953.6	$ 1,785.5	$ 5,656.6	$ 5,308.2
Segment operating expenses	559.3	555.7	1,664.5	1,634.2
Interest income, TV Azteca, net	0.0	(0.6)	0.0	0.1
Segment gross margin	1,394.3	1,230.4	3,992.1	3,673.9
Segment selling, general, administrative and development expense	124.2	94.6	347.7	317.6
Segment operating profit	1,270.1	1,135.8	3,644.4	3,356.3
Stock-based compensation expense	23.5	43.8	87.9	111.3
Other selling, general, administrative and development expense	40.8	40.5	117.3	114.5
Depreciation, amortization and accretion	442.8	448.9	1,328.6	1,344.9
Other expense	221.0	212.8	663.1	828.3
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	542.0	389.8	1,447.5	957.3
Total assets	39,307.2	33,077.2	39,307.2	33,077.2	$ 33,010.4
Impairment charges	14.0	1.8	45.1	182.4
Operating Expense
Segment Reporting Information [Line Items]
Stock-based compensation expense	0.6	1.0	2.1	2.7
Selling General Administrative And Development Expense
Segment Reporting Information [Line Items]
Stock-based compensation expense	22.9	42.8	85.8	108.6
TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		(0.6)		0.1
U.S.
Segment Reporting Information [Line Items]
Revenues	1,127.9	991.6	3,189.5	2,942.9
Asia
Segment Reporting Information [Line Items]
Revenues	312.5	323.1	922.5	904.0
EMEA
Segment Reporting Information [Line Items]
Revenues	181.5	166.6	534.0	507.5
Latin America
Segment Reporting Information [Line Items]
Revenues	331.7	304.2	1,010.6	953.8
Operating Segments \| Property
Segment Reporting Information [Line Items]
Revenues	1,921.6	1,751.6	5,556.5	5,211.4
Segment operating expenses	547.6	542.3	1,629.0	1,595.7
Segment gross margin	1,374.0	1,209.9	3,927.5	3,615.6
Segment selling, general, administrative and development expense	120.8	88.3	338.9	304.9
Segment operating profit	1,253.2	1,121.6	3,588.6	3,310.7
Total assets	38,733.9	32,708.4	38,733.9	32,708.4
Operating Segments \| Property \| TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		(0.6)		0.1
Operating Segments \| Property \| U.S.
Segment Reporting Information [Line Items]
Revenues	1,095.9	957.7	3,089.4	2,846.1
Segment operating expenses	207.5	193.3	595.4	578.4
Segment gross margin	888.4	764.4	2,494.0	2,267.7
Segment selling, general, administrative and development expense	44.5	37.9	128.4	117.1
Segment operating profit	843.9	726.5	2,365.6	2,150.6
Total assets	22,653.2	18,664.5	22,653.2	18,664.5
Operating Segments \| Property \| U.S. \| TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		0.0		0.0
Operating Segments \| Property \| Asia
Segment Reporting Information [Line Items]
Revenues	312.5	323.1	922.5	904.0
Segment operating expenses	177.9	194.7	544.2	532.7
Segment gross margin	134.6	128.4	378.3	371.3
Segment selling, general, administrative and development expense	33.1	13.5	77.4	72.8
Segment operating profit	101.5	114.9	300.9	298.5
Total assets	5,324.9	5,093.7	5,324.9	5,093.7
Operating Segments \| Property \| Asia \| TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		0.0		0.0
Operating Segments \| Property \| EMEA
Segment Reporting Information [Line Items]
Revenues	181.5	166.6	534.0	507.5
Segment operating expenses	58.6	57.5	178.9	175.1
Segment gross margin	122.9	109.1	355.1	332.4
Segment selling, general, administrative and development expense	19.7	16.2	58.1	50.6
Segment operating profit	103.2	92.9	297.0	281.8
Total assets	3,626.6	3,272.7	3,626.6	3,272.7
Operating Segments \| Property \| EMEA \| TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		0.0		0.0
Operating Segments \| Property \| Latin America
Segment Reporting Information [Line Items]
Revenues	331.7	304.2	1,010.6	953.8
Segment operating expenses	103.6	96.8	310.5	309.5
Segment gross margin	228.1	208.0	700.1	644.2
Segment selling, general, administrative and development expense	23.5	20.7	75.0	64.4
Segment operating profit	204.6	187.3	625.1	579.8
Total assets	7,129.2	5,677.5	7,129.2	5,677.5
Operating Segments \| Property \| Latin America \| TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		(0.6)		0.1
Operating Segments \| Services
Segment Reporting Information [Line Items]
Revenues	32.0	33.9	100.1	96.8
Segment operating expenses	11.7	13.4	35.5	38.5
Segment gross margin	20.3	20.5	64.6	58.3
Segment selling, general, administrative and development expense	3.4	6.3	8.8	12.7
Segment operating profit	16.9	14.2	55.8	45.6
Total assets	55.8	50.6	55.8	50.6
Operating Segments \| Services \| TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		0.0		0.0
Other
Segment Reporting Information [Line Items]
Stock-based compensation expense	23.5	43.8	87.9	111.3
Other selling, general, administrative and development expense	40.8	40.5	117.3	114.5
Depreciation, amortization and accretion	442.8	448.9	1,328.6	1,344.9
Other expense	221.0	212.8	663.1	828.3
Total assets	$ 517.5	$ 318.2	$ 517.5	$ 318.2

SUBSEQUENT EVENTS (Details)			9 Months Ended
SUBSEQUENT EVENTS (Details)	Oct. 03, 2019 USD ($)	Jun. 13, 2019	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Mar. 15, 2019
Subsequent Event [Line Items]
Proceeds from issuance of debt			$ 1,300,000,000.0	$ 1,500,000,000.0
Senior notes
Subsequent Event [Line Items]
Debt redemption price rate (as a percent)		100.00%
Purchase price as percentage of principal					101.00%
Maximum adjusted EBITDA			3.5
Subsequent Event \| Senior notes
Subsequent Event [Line Items]
Debt redemption price rate (as a percent)	100.00%
Purchase price as percentage of principal	101.00%
Maximum adjusted EBITDA	3.5
Subsequent Event \| Senior notes \| 2750% Senior Notes Due 2027
Subsequent Event [Line Items]
Long-term debt, stated interest rate (as a percent)	2.75%
Senior note public offering, amount	$ 750,000,000.0
Subsequent Event \| Senior notes \| 3700% Senior Notes Due 2049
Subsequent Event [Line Items]
Long-term debt, stated interest rate (as a percent)	3.70%
Senior note public offering, amount	$ 600,000,000.0
Proceeds from issuance of debt	$ 1,334,200,000

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Statement of Cash Flows [Abstract]
Income tax refunds	$ 9.5	$ 24.9

LEASES - ADDITIONAL INFORMATION FOR CAPITAL LEASES (Details) $ in Millions	Dec. 31, 2018 USD ($)
Lessee, Lease, Description [Line Items]
Future minimum rental payments under capital leases	$ 261.6
Amounts representing interest	82.1
Land Easements
Lessee, Lease, Description [Line Items]
Future minimum rental payments under capital leases	220.3
Amounts representing interest	$ 69.3

NOTES RECEIVABLE AND OTHER NON-CURRENT ASSETS (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Receivables [Abstract]
Long-term prepaid ground rent	$ 0.0	$ 607.5
Notes receivable	1.0	1.0
Other miscellaneous assets	247.9	354.1
Notes receivable and other non-current assets	$ 248.9	$ 962.6

LEASES - LEASE COSTS (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
LEASES - LEASE COSTS (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2019
Leases [Abstract]
Operating lease cost	$ 249.5	$ 760.3
Variable lease payments not included in lease liability	$ 67.7	$ 190.8

Label	Element	Value
Accounting Standards Update 2014-09 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 38,400,000
Accounting Standards Update 2014-09 [Member] \| Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	38,400,000
Accounting Standards Update 2016-02 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(24,700,000)
Accounting Standards Update 2016-02 [Member] \| Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (24,700,000)