Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2016	Apr. 22, 2016
Document And Entity Information [Abstract]
Entity Registrant Name	AMERICAN TOWER CORP /MA/
Entity Central Index Key	0001053507
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		424,624,797
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
CURRENT ASSETS:
Cash and cash equivalents	$ 336,403	$ 320,686	$ 323,400
Restricted cash	140,865	142,193
Accounts receivable, net	217,457	227,354
Prepaid and other current assets	341,791	306,235
Total current assets	1,036,516	996,468
PROPERTY AND EQUIPMENT, net	9,917,985	9,866,424
GOODWILL	4,123,401	4,091,805
OTHER INTANGIBLE ASSETS, net	9,813,990	9,837,876
DEFERRED INCOME TAXES	216,643	212,041
DEFERRED RENT ASSET	1,201,841	1,166,755
NOTES RECEIVABLE AND OTHER NON-CURRENT ASSETS	753,939	732,903
TOTAL	27,064,315	26,904,272	$ 25,930,194
CURRENT LIABILITIES:
Accounts payable	94,051	96,714
Accrued expenses	437,546	516,413
Distributions payable	218,420	210,027
Accrued interest	87,899	115,672
Current portion of long-term obligations	137,853	50,202
Unearned revenue	222,387	211,001
Total current liabilities	1,198,156	1,200,029
LONG-TERM OBLIGATIONS	16,884,242	17,068,807
ASSET RETIREMENT OBLIGATIONS	888,040	856,936
OTHER NON-CURRENT LIABILITIES	1,093,662	1,065,682
Total liabilities	20,064,100	20,191,454
COMMITMENTS AND CONTINGENCIES
EQUITY:
Common stock: $.01 par value; 1,000,000,000 shares authorized; 427,373,031 and 426,695,279 shares issued; and 424,563,005 and 423,885,253 shares outstanding, respectively	4,273	4,267
Additional paid-in capital	9,714,952	9,690,609
Distributions in excess of earnings	(967,718)	(998,535)
Accumulated other comprehensive loss	(1,610,592)	(1,836,996)
Treasury stock (2,810,026 shares at cost)	(207,740)	(207,740)
Total American Tower Corporation equity	6,933,249	6,651,679
Noncontrolling interest	66,966	61,139
Total equity	7,000,215	6,712,818	$ 7,431,639
TOTAL	27,064,315	26,904,272
Preferred Stock \| Convertible Preferred Stock Subject to Mandatory Redemption \| Series A Preferred Stock
EQUITY:
Preferred stock: $.01 par value: 20,000,000 authorized: 5.25%, Series A, 6,000,000 shares issued and outstanding; aggregate liquidation value of $600,000 - 5.50% Series B, 1,375,000 shares issued and outstanding, respectively; aggregate liquidation value of $1,375,000	60	60
Total equity	60	60	60
Preferred Stock \| Convertible Preferred Stock Subject to Mandatory Redemption \| Series B Preferred Stock
EQUITY:
Preferred stock: $.01 par value: 20,000,000 authorized: 5.25%, Series A, 6,000,000 shares issued and outstanding; aggregate liquidation value of $600,000 - 5.50% Series B, 1,375,000 shares issued and outstanding, respectively; aggregate liquidation value of $1,375,000	14	14
Total equity	$ 14	$ 14	$ 14

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	3 Months Ended	12 Months Ended
CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	Mar. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	427,373,031	426,695,279
Common stock, shares outstanding	424,563,005	423,885,253
Treasury stock, shares	2,810,026	2,810,026
Preferred Stock \| Convertible Preferred Stock Subject to Mandatory Redemption
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred Stock \| Convertible Preferred Stock Subject to Mandatory Redemption \| Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)	$ 0.01
Preferred stock, shares issued	6,000,000	6,000,000
Preferred stock, shares outstanding	6,000,000	6,000,000
Preferred stock, aggregate liquidation value	$ 600,000	$ 600,000
Preferred stock, dividend rate percentage (in percent)	5.25%	5.25%
Preferred Stock \| Convertible Preferred Stock Subject to Mandatory Redemption \| Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)	$ 0.01
Preferred stock, shares issued	1,375,000	1,375,000
Preferred stock, shares outstanding	1,375,000	1,375,000
Preferred stock, aggregate liquidation value	$ 1,375,000	$ 1,375,000
Preferred stock, dividend rate percentage (in percent)	5.50%	5.50%

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
REVENUES:
Property	$ 1,267,651	$ 1,062,180
Services	21,396	17,010
Total operating revenues	1,289,047	1,079,190
OPERATING EXPENSES:
Property (including stock-based compensation expense of $507 and $432, respectively)	342,290	259,257
Services (including stock-based compensation expense of $151 and $139, respectively)	9,155	5,383
Depreciation, amortization and accretion	341,634	263,520
Selling, general, administrative and development expense (including stock-based compensation expense of $27,421 and $29,290, respectively)	135,315	123,290
Other operating expenses	8,800	7,774
Total operating expenses	837,194	659,224
OPERATING INCOME	451,853	419,966
OTHER INCOME (EXPENSE):
Loss on retirement of long-term obligations	0	(3,725)
Other income (expense) (including unrealized foreign currency gains (losses) of $29,362 and ($55,468), respectively)	12,208	(54,503)
Total other expense	(141,422)	(200,602)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	310,431	219,364
Income tax provision	(29,124)	(23,872)
NET INCOME	281,307	195,492
Net income attributable to noncontrolling interest	(6,148)	(2,175)
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION STOCKHOLDERS	275,159	193,317
Dividends on preferred stock	(26,781)	(9,819)
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION COMMON STOCKHOLDERS	$ 248,378	$ 183,498
NET INCOME PER COMMON SHARE AMOUNTS:
Basic net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 0.59	$ 0.45
Diluted net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 0.58	$ 0.45
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING:
BASIC (in shares)	424,059	405,111
DILUTED (in shares)	427,888	409,399
DISTRIBUTIONS DECLARED PER COMMON SHARE	$ 0.51	$ 0.42
TV Azteca
OTHER INCOME (EXPENSE):
Interest income, TV Azteca, net of interest expense of $283 and $370, respectively	$ 2,716	$ 2,596
Interest expense	(283)	(370)
Excluding TV Azteca
OTHER INCOME (EXPENSE):
Interest income	3,534	2,964
Interest expense	$ (159,880)	$ (147,934)

CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Stock-based compensation expense	$ 28,079	$ 29,861
TV Azteca
Interest expense	283	370
Rental And Management
Stock-based compensation expense	507	432
Network Development Services
Stock-based compensation expense	151	139
Selling General Administrative And Development Expense
Stock-based compensation expense	27,421	29,290
Other Expense
Unrealized foreign currency (losses) gains	$ 29,362	$ (55,468)

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 281,307	$ 195,492
Other comprehensive income (loss):
Changes in fair value of cash flow hedges, net of tax benefit of $0 and $51, respectively	74	(942)
Reclassification of unrealized (gains) losses on cash flow hedges to net income, net of tax benefit of $0 and $24, respectively	(8)	387
Foreign currency translation adjustments, net of tax expense (benefit) of $4,188 and ($12,609), respectively	226,292	(432,961)
Other comprehensive income (loss)	226,358	(433,516)
Comprehensive income (loss)	507,665	(238,024)
Comprehensive (income) loss attributable to non-controlling interest	(6,102)	19,702
Comprehensive income (loss) attributable to American Tower Corporation stockholders	$ 501,563	$ (218,322)

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net change in fair value of cash flow hedges, tax	$ 0	$ (51)
Foreign currency translation adjustments, tax	4,188	(12,609)
Reclassification of unrealized losses on cash flow hedges to net income, tax	$ 0	$ (24)

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 281,307	$ 195,492
Adjustments to reconcile net income to cash provided by operating activities
Depreciation, amortization and accretion	341,634	263,520
Stock-based compensation expense	28,079	29,861
Loss on early retirement of long-term obligations	0	3,725
Other non-cash items reflected in statements of operations	12,451	66,309
Decrease in restricted cash	(3,005)	(28,180)
Increase in net deferred rent asset	(16,171)	(25,074)
Increase in assets	(30,535)	(2,779)
Decrease in liabilities	(56,258)	(49,304)
Cash provided by operating activities	563,512	509,930
CASH FLOWS FROM INVESTING ACTIVITIES
Payments for purchase of property and equipment and construction activities	(154,222)	(159,184)
Payments for acquisitions, net of cash acquired	(873)	(20,946)
Payment for Verizon transaction	(4,655)	(5,058,019)
Proceeds from sale of short-term investments and other non-current assets	1,184	72,684
Payments for short-term investments	0	(82,557)
Deposits, restricted cash, investments and other	(26,950)	(1,397)
Cash used for investing activities	(185,516)	(5,249,419)
CASH FLOW FROM FINANCING ACTIVITIES
Repayments of short-term borrowings, net	(8,636)	0
Borrowings under credit facilities	31,504	3,150,000
Proceeds from issuance of senior notes, net	1,247,463	0
Proceeds from term loan	0	500,000
Repayments of notes payable, credit facilities and capital leases	(1,388,613)	(2,490,771)
Distributions to noncontrolling interest holders, net	(274)	(137)
Proceeds from stock options	14,582	5,106
Distributions paid on common stock	(209,984)	(152,037)
Distributions paid on preferred stock	(26,781)	(7,875)
Proceeds from the issuance of common stock, net	0	2,440,390
Proceeds from the issuance of preferred stock, net	0	1,338,009
Deferred financing costs and other financing activities	(25,325)	(22,558)
Cash (used for) provided by financing activities	(366,064)	4,760,127
Net effect of changes in foreign currency exchange rates on cash and cash equivalents	3,785	(10,730)
NET INCREASE IN CASH AND CASH EQUIVALENTS	15,717	9,908
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	320,686	313,492
CASH AND CASH EQUIVALENTS, END OF PERIOD	336,403	323,400
Supplemental Cash Flow Elements [Abstract]
CASH PAID FOR INCOME TAXES (NET OF REFUNDS OF $3,431 AND $922, RESPECTIVELY)	19,368	14,714
CASH PAID FOR INTEREST	177,574	199,022
Decrease in accounts payable and accrued expenses for purchases of property and equipment and construction activities	22,586	26,499
Purchases of property and equipment under capital leases	$ 9,958	$ 4,394

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Distributions in Excess of Earnings	Noncontrolling Interest	Series A Preferred Stock Convertible Preferred Stock Subject to Mandatory Redemption Preferred Stock	Series B Preferred Stock Convertible Preferred Stock Subject to Mandatory Redemption Preferred Stock
BALANCE at Dec. 31, 2014	$ 4,053,352	$ 3,995	$ (207,740)	$ 5,788,786	$ (794,221)	$ (837,320)	$ 99,792	$ 60	$ 0
BALANCE (shares) at Dec. 31, 2014		399,508,751	(2,810,026)					6,000,000	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation related activity	16,591	$ 5		16,586
Stock based compensation related activity (shares)		524,880
Issuance of common stock	2,440,390	$ 259		2,440,131
Issuance of common stock (shares)		25,850,000
Issuance of preferred stock	1,338,009			1,337,995				$ 0	$ 14
Issuance of preferred stock (shares)								0	1,375,000
Changes in fair value of cash flow hedges, net of tax	(942)				(909)		(33)
Reclassification of unrealized gains on cash flow hedges to net income	387				372		15
Foreign currency translation adjustment, net of tax	(432,961)				(411,102)		(21,859)
Distributions to noncontrolling interest	(137)						(137)
Common stock dividends/distributions declared	(178,542)					(178,542)
Net income	195,492					193,317	2,175
BALANCE at Mar. 31, 2015	7,431,639	$ 4,259	$ (207,740)	9,583,498	(1,205,860)	(822,545)	79,953	$ 60	$ 14
BALANCE (shares) at Mar. 31, 2015		425,883,631	(2,810,026)					6,000,000	1,375,000
BALANCE at Dec. 31, 2015	6,712,818	$ 4,267	$ (207,740)	9,690,609	(1,836,996)	(998,535)	61,139	$ 60	$ 14
BALANCE (shares) at Dec. 31, 2015		426,695,279	(2,810,026)					6,000,000	1,375,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation related activity	24,349	$ 6		24,343
Stock based compensation related activity (shares)		677,752
Changes in fair value of cash flow hedges, net of tax	74				74
Reclassification of unrealized gains on cash flow hedges to net income	(8)				(8)
Foreign currency translation adjustment, net of tax	226,292				226,338		(46)
Distributions to noncontrolling interest	(275)						(275)
Common stock dividends/distributions declared	(217,561)					(217,561)
Preferred stock dividends declared	(26,781)					(26,781)
Net income	281,307					275,159	6,148
BALANCE at Mar. 31, 2016	$ 7,000,215	$ 4,273	$ (207,740)	$ 9,714,952	$ (1,610,592)	$ (967,718)	$ 66,966	$ 60	$ 14
BALANCE (shares) at Mar. 31, 2016		427,373,031	(2,810,026)					6,000,000	1,375,000

DESCRIPTION OF BUSINESS, BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
DESCRIPTION OF BUSINESS, BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	DESCRIPTION OF BUSINESS, BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES American Tower Corporation (together with its subsidiaries, “ATC” or the “Company”) is one of the largest global real estate investment trusts and a leading independent owner, operator and developer of multitenant communications real estate. The Company’s primary business is the leasing of space on 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, which the Company refers to as its property operations. Additionally, the Company offers tower-related services, referred to as its services operations, in the United States, including site acquisition, zoning and permitting and structural analysis, which primarily support its site leasing business, including the addition of new tenants and equipment on its sites. The Company’s portfolio primarily consists of towers it owns and towers it operates pursuant to long-term lease arrangements, as well as distributed antenna system (“DAS”) networks, which provide seamless coverage solutions for in-building and outdoor wireless environments. In addition to the communications sites in its portfolio, the Company manages rooftop and tower sites for property owners under various contractual arrangements. The Company also holds property interests that it leases to communications service providers and third-party tower operators. ATC is a holding company that conducts its operations through its directly and indirectly owned subsidiaries and its joint ventures. ATC’s principal domestic operating subsidiaries are American Towers LLC and SpectraSite Communications, LLC. ATC conducts its international operations primarily through its subsidiary, American Tower International, Inc., which in turn conducts operations through its various international holding and operating subsidiaries and joint ventures. The Company operates as a real estate investment trust for U.S. federal income tax purposes (“REIT”). Accordingly, the Company generally is not subject to U.S. federal income taxes on income generated by its U.S. REIT operations, including the income derived from leasing space on its towers, as the Company receives a dividends paid deduction for distributions to stockholders that generally offsets its income and gains. However, the Company remains obligated to pay U.S. federal income taxes on earnings from its domestic taxable REIT subsidiaries (“TRSs”). In addition, the Company’s international assets and operations, regardless of their designation for U.S. tax purposes, continue to be subject to taxation in the foreign jurisdictions where those assets are held or those operations are conducted. The use of TRSs enables the Company to continue to engage in certain businesses while complying with REIT qualification requirements. The Company may, from time to time, change the election of previously designated TRSs to be included as part of the REIT. As of March 31, 2016, the Company’s U.S. REIT-qualified businesses included its U.S. tower leasing business, most of its operations in Costa Rica, Germany and Mexico and a majority of its services segment and indoor DAS networks business. The accompanying consolidated and condensed consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission. The financial information included herein is unaudited; however, the Company believes that all adjustments 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, 2015 (the “2015 Form 10-K”). The results of operations for the three months ended March 31, 2016 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 or cost method, depending upon the Company’s ability to exercise significant influence over operating and financial policies. All intercompany accounts and transactions have been eliminated. Significant Accounting Policies—The Company’s significant accounting policies are described in note 1 to the Company’s consolidated financial statements included in the 2015 Form 10-K. There have been no material changes to the Company’s significant accounting policies during the first three months of 2016. Accounting Standards Updates—In May 2014, the Financial Accounting Standards Board (the “FASB”) issued new revenue recognition guidance, which requires an entity to recognize revenue in an amount that reflects the consideration to which the entity expects to be entitled in exchange for the transfer of promised goods or services to customers. The standard will replace most existing revenue recognition guidance and will become effective for the Company on January 1, 2018. Early adoption is permitted for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2016. The standard permits the use of either the retrospective or cumulative effect transition method. Leases are not included in the scope of this standard. The Company is evaluating the impact this standard will have on its financial statements. In January 2016, the FASB issued new guidance on the recognition and measurement of financial assets and financial liabilities. The guidance amends certain aspects of recognition, measurement, presentation and disclosure of financial instruments. This standard is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2017. The Company does not expect the adoption of this guidance to have a material effect on the Company’s financial statements. In February 2016, the FASB issued new guidance on the accounting for leases. The guidance amends the existing accounting standards for lease accounting, including the requirement that lessees recognize assets and liabilities for leases with terms greater than twelve months in the statement of financial position. Under the new guidance, lessor accounting is largely unchanged. This guidance is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2018. The Company is evaluating the impact this standard will have on its financial statements. In March 2016, the FASB issued new guidance on the accounting for share-based payment transactions. The guidance amends the accounting for taxes related to stock-based compensation, including how excess tax benefits and a company’s payments for tax withholdings should be classified. This guidance is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2016. The Company does not expect the adoption of this guidance to have a material effect on its financial statements.

GOODWILL AND OTHER INTANGIBLE ASSETS

3 Months Ended

Mar. 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL AND OTHER INTANGIBLE ASSETS

The Company had no material changes in the carrying value of goodwill during the three months ended March 31, 2016. The effect of foreign currency translation on goodwill for the non-U.S. segments was $31.6 million.

The Company’s other intangible assets subject to amortization consisted of the following (in thousands):



		As of March 31, 2016							As of December 31, 2015
	Estimated Useful Lives	Gross Carrying Value		Accumulated Amortization			Net Book Value		Gross Carrying Value		Accumulated Amortization			Net Book Value
	(years)	(in thousands)
Acquired network location intangibles (1)	Up to 20	$	4,019,860	$	(1,109,770	)	$	2,910,090	$	3,980,281	$	(1,052,393	)	$	2,927,888
Acquired customer-related intangibles	15-20	8,747,912		(1,879,003		)	6,868,909		8,640,554		(1,763,853		)	6,876,701
Acquired licenses and other intangibles	3-20	26,213		(1,707		)	24,506		28,293		(5,486		)	22,807
Economic Rights, TV Azteca	70	21,799		(11,314		)	10,485		21,688		(11,208		)	10,480
Total other intangible assets		$	12,815,784	$	(3,001,794	)	$	9,813,990	$	12,670,816	$	(2,832,940	)	$	9,837,876

_______________


(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 customer-related intangibles typically represent the value to the Company of customer 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 customer-related intangibles on a straight-line basis over their estimated useful lives. As of March 31, 2016, the remaining weighted average amortization period of the Company’s intangible assets, excluding the TV Azteca Economic Rights detailed in note 5 to the Company’s consolidated financial statements included in the 2015 Form 10-K, was 16 years. Amortization of intangible assets for the three months ended March 31, 2016 and 2015 was $151.8 million and $110.5 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 (in millions):



Fiscal Year
Remainder of 2016	$	451.4
2017	603.8
2018	602.8
2019	600.4
2020	583.3
2021	574.4

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

LONG-TERM OBLIGATIONS

3 Months Ended

Mar. 31, 2016

Long-term Debt, Excluding Current Maturities [Abstract]

LONG-TERM OBLIGATIONS

Outstanding amounts under the Company’s long-term obligations, reflecting discounts, premiums and debt issuance costs, consisted of the following (in thousands):



	As of
	March 31, 2016			December 31, 2015			Maturity Date
Series 2013-1A securities (1)	$	497,769		$	497,478		March 15, 2018
Series 2013-2A securities (2)	1,289,083			1,288,689			March 15, 2023
Series 2015-1 notes (3)	346,474			346,262			June 15, 2020
Series 2015-2 notes (4)	518,941			518,776			June 16, 2025
2012 GTP notes (5)	279,555			281,902			Various
Unison notes (6)	201,492			201,930			Various
Shareholder loans (7)	145,081			145,540			Various
BR Towers debentures (8)	94,886			85,219			October 15, 2023
Colombian credit facility (9)	60,531			59,640			April 24, 2021
South African facility (10)	52,874			53,175			December 17, 2020
Brazil credit facility (11)	24,021			21,868			January 15, 2022
Indian working capital facility (12)	—			8,752			N/A
Total American Tower subsidiary debt	3,510,707			3,509,231

2013 Credit Facility	31,865			1,225,000			June 28, 2019
Term Loan	1,993,915			1,993,601			January 29, 2021
2014 Credit Facility	1,830,000			1,980,000			January 29, 2021
4.500% senior notes	997,974			997,693			January 15, 2018
3.40% senior notes	999,804			999,769			February 15, 2019
7.25% senior notes	296,502			296,242			May 15, 2019
2.800% senior notes	743,916			743,557			June 1, 2020
5.050% senior notes	697,381			697,216			September 1, 2020
3.300% senior notes	743,900			—			February 15, 2021
3.450% senior notes	643,024			642,786			September 15, 2021
5.900% senior notes	497,307			497,188			November 1, 2021
4.70% senior notes	695,545			695,374			March 15, 2022
3.50% senior notes	988,365			987,966			January 31, 2023
5.00% senior notes	1,003,403			1,003,453			February 15, 2024
4.000% senior notes	739,322			739,057			June 1, 2025
4.400% senior notes	494,911			—			February 15, 2026
Total American Tower Corporation debt	13,397,134			13,498,902
Other debt, including capital lease obligations	114,254			110,876
Total	17,022,095			17,119,009
Less current portion of long-term obligations	(137,853		)	(50,202		)
Long-term obligations	$	16,884,242		$	17,068,807

_______________

(1) Maturity date represents anticipated repayment date; final legal maturity is March 15, 2043.

(2) Maturity date represents anticipated repayment date; final legal maturity is March 15, 2048.

(3) Maturity date represents anticipated repayment date; final legal maturity is June 15, 2045.

(4) Maturity date represents anticipated repayment date; final legal maturity is June 15, 2050.


(5)	Secured debt assumed by the Company in connection with the acquisition of MIP Tower Holdings LLC (“MIPT”). Anticipated repayment dates begin March 15, 2017.


(6)	Secured debt assumed by the Company in connection with the acquisition of certain legal entities from Unison Holdings LLC and Unison Site Management II, L.L.C. Anticipated repayment dates begin April 15, 2017; final legal maturity date is April 15, 2040.


(7)	Reflects balances owed to the Company’s joint venture partners in Ghana and Uganda. The Ghana loan is denominated in Ghanaian Cedi and the Uganda loan is denominated in U.S. Dollars.


(8)	Publicly issued debentures assumed by the Company in connection with the acquisition of BR Towers S.A. Denominated in Brazilian Reais (“BRL”).

(9) Denominated in Colombian Pesos.


(10)	Denominated in South African Rand.

(11) Denominated in BRL.

(12) Denominated in Indian Rupee (“INR”).

Current portion of long-term obligations—The Company’s current portion of long-term obligations primarily includes $97.7 million outstanding under the Secured Tower Cellular Site Revenue Notes, Series 2012-1A and Series 2012-2A (included in the 2012 GTP notes) assumed in connection with the acquisition of MIPT.

3.300% Senior Notes and 4.400% Senior Notes Offering—On January 12, 2016, the Company completed a registered public offering of $750.0 million aggregate principal amount of 3.300% senior unsecured notes due 2021 (the “3.300% Notes”) and $500.0 million aggregate principal amount of 4.400% senior unsecured notes due 2026 (the “4.400% Notes”). The net proceeds from this offering were approximately $1,237.2 million, after deducting commissions and estimated expenses. The Company used the proceeds to repay existing indebtedness under its multicurrency senior unsecured revolving credit facility entered into in June 2013, as amended (the “2013 Credit Facility”) and for general corporate purposes.

The 3.300% Notes will mature on February 15, 2021 and bear interest at a rate of 3.300% per annum. The 4.400% Notes will mature on February 15, 2026 and bear interest at a rate of 4.400% per annum. Accrued and unpaid interest on the notes will be payable in U.S. Dollars semi-annually in arrears on February 15 and August 15 of each year, beginning on August 15, 2016. Interest on the notes is computed on the basis of a 360-day year comprised of twelve 30-day months and commenced accruing on January 12, 2016.

The Company may redeem each series of 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 3.300% Notes on or after January 15, 2021 or the 4.400% Notes on or after November 15, 2025, 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 supplemental indenture, it may be required to repurchase all of the notes at a purchase price equal to 101% of the principal amount of the 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 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 such liens does not exceed 3.5x Adjusted EBITDA, as defined in the supplemental indenture.

Bank Facilities

2013 Credit Facility—During the three months ended March 31, 2016, the Company repaid an aggregate of $1.2 billion of revolving indebtedness under the 2013 Credit Facility. On March 30, 2016, one of the Company’s German subsidiaries borrowed EUR 28.0 million ($31.5 million on the date of borrowing) under the 2013 Credit Facility as a subsidiary borrower, the proceeds of which were used to partially fund an acquisition in Germany subsequent to the end of the period.

2014 Credit Facility—During the three months ended March 31, 2016, the Company repaid an aggregate of $150.0 million of revolving indebtedness under its senior unsecured revolving credit facility entered into in January 2012 and amended and restated in September 2014, as amended (the “2014 Credit Facility”).

As of March 31, 2016, the key terms under the 2013 Credit Facility, the 2014 Credit Facility and the Company’s unsecured term loan entered into in October 2013, as amended (the “Term Loan”) are 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	$	31.9	$	3.2	June 28, 2019 (3)	1.250	%	0.150	%
2014 Credit Facility	$	1,830.0	$	7.4	January 29, 2021 (3)	1.250	%	0.150	%
Term Loan	$	2,000.0	N/A		January 29, 2021	1.250	%	N/A

_______________

(1) LIBOR means the London Interbank Offered Rate.

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

(3) Subject to two optional renewal periods.

FAIR VALUE MEASUREMENTS

3 Months Ended

Mar. 31, 2016

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 value of the Company’s financial assets and liabilities that are required to be measured on a recurring basis at fair value was as follows (in thousands):



	March 31, 2016						December 31, 2015
	Fair Value Measurements Using				Assets/Liabilities at Fair Value		Fair Value Measurements Using				Assets/Liabilities at Fair Value
	Level 2		Level 3		Assets/Liabilities at Fair Value		Level 2		Level 3		Assets/Liabilities at Fair Value
Assets:
Interest rate swap agreements	$	790	—		$	790	$	692	—		$	692
Embedded derivative in lease agreement	—		$	13,955	$	13,955	—		$	14,176	$	14,176
Liabilities:
Acquisition-related contingent consideration	—		$	11,816	$	11,816	—		$	12,436	$	12,436

During the three months ended March 31, 2016, the Company has not made any changes to the methods used to measure the fair value of its interest rate swap agreements, the embedded derivative in one of its lease agreements and acquisition-related contingent consideration. The changes in fair value during the three months ended March 31, 2016 and 2015 were not material to the consolidated financial statements. As of March 31, 2016, the Company estimated that the value of all potential acquisition-related contingent consideration required payments to be between zero and $25.7 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. During the three months ended March 31, 2016 and 2015, the Company did not record any asset impairment charges.

There were no other items measured at fair value on a nonrecurring basis during the three months ended March 31, 2016.

Fair Value of Financial Instruments—The Company’s financial instruments for which the carrying value reasonably approximates fair value at March 31, 2016 and December 31, 2015 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 March 31, 2016 and December 31, 2015, the carrying value of long-term obligations, including the current portion, was $17.0 billion and $17.1 billion, respectively. As of March 31, 2016, the fair value of long-term obligations, including the current portion, was $17.6 billion, of which $10.1 billion was measured using Level 1 inputs and $7.5 billion was measured using Level 2 inputs. As of December 31, 2015, the fair value of long-term obligations, including the current portion, was $17.4 billion, of which $8.7 billion was measured using Level 1 inputs and $8.7 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	3 Months Ended
INCOME TAXES	Mar. 31, 2016
Income Tax Expense (Benefit), Continuing Operations [Abstract]
INCOME TAXES	INCOME TAXES The Company provides for income taxes at the end of each interim period based on the estimated effective tax rate 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 effective tax rate is determined. As a REIT, the Company continues to be subject to income taxes on the income of its TRSs and income taxes in foreign jurisdictions where it conducts international operations. 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 REIT 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 positive and negative evidence to estimate if sufficient future taxable income will be generated to use the existing deferred tax assets. As of March 31, 2016 and December 31, 2015, the total unrecognized tax benefits that would impact the effective tax rate, if recognized, were approximately $35.5 million and $28.1 million, respectively. The amount of unrecognized tax benefits during the three months ended March 31, 2016 includes additions to the Company’s existing tax positions of $6.5 million and foreign currency fluctuations of $0.9 million. The Company expects the unrecognized tax benefits 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 2015 Form 10-K. The impact of the amount of these changes to previously recorded uncertain tax positions could range from zero to $14.5 million. The Company recorded penalties and income tax-related interest expense during the three months ended March 31, 2016 and 2015 of $3.2 million and $0.9 million, respectively. As of March 31, 2016 and December 31, 2015, the total amount of accrued income tax related interest and penalties included in the consolidated balance sheets was $23.8 million and $20.2 million, respectively.

STOCK-BASED COMPENSATION

3 Months Ended

Mar. 31, 2016

Share-based Compensation, Allocation and Classification in Financial Statements [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 (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 in the case of 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 March 31, 2016, the Company had the ability to grant stock-based awards with respect to an aggregate of 9.4 million shares of common stock under the 2007 Plan.

The Company recognized stock-based compensation expense of $28.1 million and $29.9 million during the three months ended March 31, 2016 and 2015, respectively. The Company capitalized stock-based compensation expense of $0.7 million and $0.5 million during the three months ended March 31, 2016 and 2015, respectively, as property and equipment.

Stock Options—The fair value of each option granted during the three months ended March 31, 2016 was estimated on the date of grant using the Black-Scholes option pricing model based on the assumptions noted in the table below. The expected life of stock options (estimated period of time outstanding) was estimated using the vesting term and historical exercise behavior of the Company’s employees. The risk-free interest rate was based on the U.S. Treasury yield with a term that approximated the estimated life in effect at the accounting measurement date. The expected volatility of the underlying stock price was based on historical volatility for a period equal to the expected life of the stock options. The expected annual dividend yield was the Company’s best estimate of expected future dividend yield.

Key assumptions used to apply this pricing model were as follows:



Range of risk-free interest rate		1.45% - 1.73%
Weighted average risk-free interest rate		1.45%
Range of expected life of stock options		4.5 - 5.2 years
Range of expected volatility of the underlying stock price		20.64% - 21.45%
Weighted average expected volatility of underlying stock price		21.45%
Range of expected annual dividend yield		1.85% - 2.40%

The weighted average grant date fair value per share during the three months ended March 31, 2016 was $14.56. As of March 31, 2016, total unrecognized compensation expense related to unvested stock options was $39.8 million and is expected to be recognized over a weighted average period of approximately three years.

The Company’s option activity for the three months ended March 31, 2016 was as follows:



	Number of Options
Outstanding as of January 1, 2016	7,680,819
Granted	1,132,596
Exercised	(262,877	)
Expired	(500	)
Outstanding as of March 31, 2016	8,550,038

Restricted Stock Units—As of March 31, 2016, total unrecognized compensation expense related to unvested RSUs granted under the 2007 Plan was $120.7 million and is expected to be recognized over a weighted average period of approximately three years.

Performance-Based Restricted Stock Units—During the three months ended March 31, 2016, the Compensation Committee granted an aggregate of 169,340 PSUs to its executive officers and established the performance metrics for this award (the “2016 PSUs”). During the three months ended March 31, 2015, the Compensation Committee granted an aggregate of 70,135 PSUs to its executive officers and established the performance metric for this award (the “2015 PSUs”). Threshold, target and maximum parameters were established for the metrics for a three-year performance period with respect to the 2016 PSUs and for each year in the three-year performance period with respect to the 2015 PSUs and will be used to calculate the number of shares that will be issuable when the award vests, which may range from zero to 200% of the target amount. At the end of the 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 the performance period, subject generally to the executive’s continued employment. PSUs will accrue dividend equivalents prior to vesting, which will be paid out only in respect of shares actually vested.

The performance metric related to the 2015 PSUs is tied to year-over-year growth, and actual results for the metric cannot be determined until the end of each respective fiscal year. As a result, as of March 31, 2016, the Company was unable to determine the annual target for the third year of the performance period for this award. Accordingly, an aggregate of 23,377 PSUs were not included in the table below.

Restricted Stock Units and Performance-Based Restricted Stock Units—The Company’s RSU and PSU activity for the three months ended March 31, 2016 was as follows:



	RSUs		PSUs
Outstanding as of January 1, 2016 (1)	1,656,993		33,377
Granted (2)	765,607		192,719
Vested	(623,111	)	—
Forfeited	(21,573	)	—
Outstanding as of March 31, 2016	1,777,916		226,096

_______________


(1)	PSUs represent the shares issuable for the 2015 PSUs at the end of the three-year performance cycle based on exceeding the performance metric for the first year’s performance period.


(2)	PSUs represent the target number of shares issuable at the end of the three-year performance cycle attributable to the second year’s performance period for the 2015 PSUs and the target number of shares issuable at the end of the three-year performance cycle for the 2016 PSUs.

During the three months ended March 31, 2016, the Company recorded $0.8 million 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 March 31, 2016 was $18.9 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.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

EQUITY

3 Months Ended

Mar. 31, 2016

Stockholders' Equity Attributable to Parent [Abstract]

EQUITY

Series A Preferred Stock—The Company has 6,000,000 shares of its 5.25% Mandatory Convertible Preferred Stock, Series A, par value $0.01 per share (the “Series A Preferred Stock”) outstanding, which were issued in May 2014.

Unless converted or redeemed earlier, each share of the Series A Preferred Stock will automatically convert on May 15, 2017, into between 0.9174 and 1.1468 shares of the Company’s common stock, depending on the applicable market value of the Company’s common stock and subject to anti-dilution adjustments. Subject to certain restrictions, at any time prior to May 15, 2017, holders of the Series A Preferred Stock may elect to convert all or a portion of their shares into common stock at the minimum conversion rate then in effect.

Dividends on shares of the Series A Preferred Stock are payable on a cumulative basis when, as and if declared by the Company’s Board of Directors at an annual rate of 5.25% on the liquidation preference of $100.00 per share, on February 15, May 15, August 15 and November 15 of each year, commencing on August 15, 2014 to, and including, May 15, 2017.

Series B Preferred Stock—The Company has 13,750,000 depositary shares, each representing a 1/10th interest in a share of its 5.50% Mandatory Convertible Preferred Stock, Series B, par value $0.01 per share (the “Series B Preferred Stock” and, together with the Series A Preferred Stock, the “Mandatory Convertible Preferred Stock”) outstanding, which were issued in March 2015.

Unless converted or redeemed earlier, each share of the Series B Preferred Stock will automatically convert on February 15, 2018, into between 8.5911 and 10.3093 shares of the Company’s common stock, depending on the applicable market value of the Company’s common stock and subject to anti-dilution adjustments. Subject to certain restrictions, at any time prior to February 15, 2018, holders of the Series B Preferred Stock may elect to convert all or a portion of their shares into common stock at the minimum conversion rate then in effect.

Dividends on shares of the Series B Preferred Stock are payable on a cumulative basis when, as and if declared by the Company’s Board of Directors at an annual rate of 5.50% on the liquidation preference of $1,000.00 per share (and, correspondingly, $100.00 per share with respect to the depositary shares) on February 15, May 15, August 15 and November 15 of each year, commencing on May 15, 2015 to, and including, February 15, 2018.

The Company may pay dividends in cash or, subject to certain limitations, in shares of common stock or any combination of cash and shares of common stock. The terms of the Mandatory Convertible Preferred Stock provide that, unless full cumulative dividends have been paid or set aside for payment on all outstanding Mandatory Convertible Preferred Stock for all prior dividend periods, no dividends may be declared or paid on common stock.

Sales of Equity Securities—The Company receives proceeds from the sale of its equity securities pursuant its employee stock purchase plan and upon exercise of stock options granted under its equity incentive plan. During the three months ended March 31, 2016, the Company received an aggregate of $14.6 million in proceeds upon exercises of stock options.

Distributions—During the three months ended March 31, 2016, the Company declared or paid the following cash distributions:



Declaration Date	Payment Date	Record Date	Distribution per share		Aggregate Payment Amount (in millions)
Common Stock
December 3, 2015	January 13, 2016	December 16, 2015	$	0.49	$	207.7
March 9, 2016	April 28, 2016	April 12, 2016	$	0.51	$	216.5

Series A Preferred Stock
January 14, 2016	February 16, 2016	February 1, 2016	$	1.3125	$	7.9

Series B Preferred Stock
January 14, 2016	February 16, 2016	February 1, 2016	$	13.75	$	18.9

The Company accrues distributions on unvested restricted stock units, which are payable upon vesting. As of March 31, 2016, the amount accrued for distributions payable related to unvested restricted stock units was $3.9 million. During the three months ended March 31, 2016, the Company paid $2.3 million of distributions upon the vesting of restricted stock units. 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.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(31))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(d))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

+ Details

EARNINGS PER COMMON SHARE

3 Months Ended

Mar. 31, 2016

Earnings Per Share [Abstract]

EARNINGS PER COMMON SHARE

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



	Three Months Ended March 31,
	2016			2015
Net income attributable to American Tower Corporation stockholders	$	275,159		$	193,317
Dividends on preferred stock	(26,781		)	(9,819		)
Net income attributable to American Tower Corporation common stockholders	248,378			183,498
Basic weighted average common shares outstanding	424,059			405,111
Dilutive securities	3,829			4,288
Diluted weighted average common shares outstanding	427,888			409,399
Basic net income attributable to American Tower Corporation common stockholders per common share	$	0.59		$	0.45
Diluted net income attributable to American Tower Corporation common stockholders per common share	$	0.58		$	0.45

Shares Excluded From Dilutive Effect—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 March 31,
	2016	2015
Restricted stock awards	152	3
Stock options	2,322	501
Preferred stock	17,413	9,194

COMMITMENTS AND CONTINGENCIES	3 Months Ended
COMMITMENTS AND CONTINGENCIES	Mar. 31, 2016
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 provides for the lease, sublease or management of 11,286 wireless communications sites from Verizon 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 right 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 each 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 Inc. (“AT&T”), that currently provides for the lease or sublease of approximately 2,370 towers from AT&T with the lease commencing between December 2000 and August 2004. Substantially all of the towers are part of the securitization transaction entered into in 2013. 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 March 31, 2016, the Company has purchased an aggregate of 60 of the subleased towers upon expiration of the applicable agreement. The aggregate purchase option price for the remaining towers leased and subleased is $713.4 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 purchased by the Company prior to June 30, 2020, AT&T will continue to lease the reserved space 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. For all such sites purchased by the Company subsequent to June 30, 2020, AT&T has the right to continue to lease the reserved space for successive one-year terms at a rent equal to the lesser of the agreed upon market rate and the then-current monthly fee, which is subject to an annual increase based on changes in the U.S. Consumer Price Index. ALLTEL Transaction—In December 2000, the Company entered into an agreement with ALLTEL, 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 has the option to purchase each tower at the expiration of the applicable sublease. The Company will exercise the purchase options for approximately 1,525 towers in a single closing to occur on or before November 30, 2016. The purchase price per tower as of the original closing date was $27,500 and will accrete at a rate of 3% per annum through the expiration of the applicable sublease. The aggregate purchase option price for the subleased towers was $75.8 million as of March 31, 2016. The purchase price would be payable in cash or, at Verizon Wireless’s or its assignee’s option, as applicable, with 769 shares of the Company’s common stock per tower. 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. The Company evaluates the circumstances of each notification based on the information available and records a liability for any potential outcome that is probable or more likely than not unfavorable if the liability is also reasonably estimable.

ACQUISITIONS

3 Months Ended

Mar. 31, 2016

Business Combination, Description [Abstract]

ACQUISITIONS

During the three months ended March 31, 2016, the Company adopted new guidance on the accounting for measurement-period adjustments related to business combinations. This guidance requires that an acquirer make adjustments to the provisional amounts recognized at acquisition date with a corresponding adjustment to goodwill in the current period. Additionally, the effects on earnings of all measurement-period adjustments are included in current period earnings.

The Company did not complete any material acquisitions during the three months ended March 31, 2016. In addition, during the three months ended March 31, 2016, there were no adjustments made to the preliminary purchase price allocations for acquisitions consummated in 2015.

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. Acquisition and merger related expenses may include finder’s fees, advisory, legal, accounting, valuation and other professional or consulting fees, fair value adjustments to contingent consideration and general administrative costs directly related to the transaction. Integration costs include incremental and non-recurring costs necessary to convert data, retain employees and otherwise enable the Company to operate new businesses efficiently. The Company records acquisition and merger related expenses, as well as integration costs, in Other operating expenses in the consolidated statements of operations.

The Company recorded acquisition and merger related expenses and integration costs as follows (in thousands):



	Three Months Ended March 31,
	2016		2015
Acquisition and merger related expenses	$	985	$	2,966
Integration costs	$	3,271	$	1,755

Pro Forma Consolidated Results

The following table presents the unaudited pro forma financial results as if the acquisition of (i) the exclusive right to lease, acquire or otherwise operate and manage approximately 11,500 wireless communications sites from Verizon in the United States, (ii) over 4,700 sites from Bharti Airtel Limited (“Airtel”) in Nigeria and (iii) nearly 5,500 sites from TIM Celular S.A. in Brazil, had occurred on January 1, 2015. Management relied on various estimates and assumptions due to the fact that some of the sites were never operated as a business and were utilized solely by the seller as a component of their network infrastructure. As a result, historical operating results may not be available. 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 March 31, 2015
Pro forma revenues	$	1,263,174
Pro forma net income attributable to American Tower Corporation common stockholders	$	150,024
Pro forma net income per common share amounts:
Basic net income attributable to American Tower Corporation common stockholders	$	0.35
Diluted net income attributable to American Tower Corporation common stockholders	$	0.35

Other Signed Acquisitions

Viom—On October 21, 2015, the Company, through its wholly owned subsidiary, ATC Asia Pacific Pte. Ltd. (“ATC Asia”), entered into a definitive agreement (the “Share Purchase Agreement”) with Viom Networks Limited (“Viom”), a telecommunications infrastructure company that owns and operates over 42,000 wireless communications towers and 200 indoor DAS networks in India, and certain existing Viom shareholders, including the current managing shareholder, SREI Infrastructure Finance Limited, several other minority shareholders and Tata Teleservices Limited (collectively, the “Selling Shareholders”), to acquire a 51% controlling ownership interest in Viom from the Selling Shareholders for cash consideration of 76.4 billion INR ($1.1 billion at the date of acquisition), subject to certain adjustments (the “Viom Acquisition”). The Viom Acquisition closed on April 21, 2016 (see note 14). The Company expects that it will consolidate the full financial results for Viom.

On October 21, 2015, ATC Asia also entered into a shareholders agreement (the “Shareholders Agreement”) with Viom and certain remaining Viom shareholders, including Tata Sons Limited, Tata Teleservices Limited, IDFC Private Equity Fund III, Macquarie SBI Investments Pte Limited and SBI Macquarie Infrastructure Trust (collectively, the “Remaining Shareholders”). The Shareholders Agreement became effective on the closing date of the Viom Acquisition. The Shareholders Agreement provides that, among other things, the Remaining Shareholders will have certain governance, anti-dilution and contractual rights. The Remaining Shareholders will have put options and ATC Asia will have a call option subject to the time periods and conditions outlined in the Shareholders Agreement.

Airtel Tanzania—On March 17, 2016, the Company entered into a definitive agreement with Airtel, through its subsidiary company Airtel Tanzania Limited (“Airtel Tanzania”), pursuant to which the Company may acquire approximately 1,350 of Airtel Tanzania’s communications towers in Tanzania, for total consideration of approximately $179.0 million, subject to customary adjustments. Under the agreement, the Company may pay additional consideration to acquire up to approximately 100 additional sites currently in development. The Company expects to close the transaction during the second quarter of 2016, subject to customary closing conditions and regulatory approval.

- Definition

The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1497-128463

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1490-128463

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e7008-128479

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1486-128463

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1524-128463

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e7000-128479

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4922-128472

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4934-128472

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4926-128472

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 4A
-URI http://asc.fasb.org/extlink&oid=73530397&loc=SL65897772-128472

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1383-128463

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6996-128479

+ Details

BUSINESS SEGMENTS

3 Months Ended

Mar. 31, 2016

Segment Reporting, Measurement Disclosures [Abstract]

BUSINESS SEGMENTS

In 2015, as a result of recent investment activity, including signed acquisitions, the Company reviewed and changed its reportable segments to divide its international segment into three regional segments: Asia property, Europe, Middle East and Africa (“EMEA”) property, and Latin America property, resulting in five total segments. The change in reportable segments had no impact on the Company’s consolidated and condensed consolidated financial statements for any periods. However, certain expenses previously reflected in segment selling, general, administrative and development expense have been reclassified and are now reflected as Other selling, general, administrative and development expense. Historical financial information included in this Quarterly Report on Form 10-Q has been adjusted to reflect the change in reportable 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 March 31, 2016, consisted of the following:


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


•	Asia: property operations in India;


•	EMEA: property operations in Germany, Ghana, Nigeria, South Africa and Uganda; and


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

The Company has applied the aggregation criteria to operations within the EMEA and Latin America property operating segments on a basis consistent with management’s review of information and performance evaluations of these regions.

The Company’s services segment offers tower-related services in the United States, including site acquisition, zoning and permitting services and structural analysis services, 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 the property operating segments and requires different resources, skill sets and marketing strategies.

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 2015 Form 10-K. 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, the Latin America property segment gross margin and segment operating profit also include Interest income, 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 interest 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 months ended March 31, 2016 and 2015 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, as the amounts are not utilized in assessing each segment’s performance.



	Property								Total Property		Services		Other		Total
Three Months Ended March 31, 2016	U.S.		Asia		EMEA		Latin America		Total Property		Services		Other		Total
	(in thousands)
Segment revenues	$	851,744	$	63,216	$	129,640	$	223,051	$	1,267,651	$	21,396			$	1,289,047
Segment operating expenses (1)	177,722		33,080		55,659		75,322		341,783		9,004				350,787
Interest income, TV Azteca, net	—		—		—		2,716		2,716		—				2,716
Segment gross margin	674,022		30,136		73,981		150,445		928,584		12,392				940,976
Segment selling, general, administrative and development expense (1)	37,286		6,576		16,152		14,584		74,598		2,916				77,514
Segment operating profit	$	636,736	$	23,560	$	57,829	$	135,861	$	853,986	$	9,476			$	863,462
Stock-based compensation expense													$	28,079	28,079
Other selling, general, administrative and development expense													30,380		30,380
Depreciation, amortization and accretion													341,634		341,634
Other expense (2)													152,938		152,938
Income from continuing operations before income taxes															$	310,431
Total assets	$	19,110,950	$	698,798	$	2,327,461	$	4,668,298	$	26,805,507	$	61,117	$	197,691	$	27,064,315

_______________


(1)	Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $0.7 million and $27.4 million, respectively.


(2)	Primarily includes interest expense.



	Property								Total Property		Services		Other		Total
Three Months Ended March 31, 2015	U.S.		Asia		EMEA		Latin America		Total Property		Services		Other		Total
	(in thousands)
Segment revenues	$	717,880	$	57,127	$	75,801	$	211,372	$	1,062,180	$	17,010			$	1,079,190
Segment operating expenses (1)	133,032		29,660		28,515		67,618		258,825		5,244				264,069
Interest income, TV Azteca, net	—		—		—		2,596		2,596		—				2,596
Segment gross margin	584,848		27,467		47,286		146,350		805,951		11,766				817,717
Segment selling, general, administrative and development expense (1)	26,822		6,829		8,859		17,262		59,772		3,436				63,208
Segment operating profit	$	558,026	$	20,638	$	38,427	$	129,088	$	746,179	$	8,330			$	754,509
Stock-based compensation expense													$	29,861	29,861
Other selling, general, administrative and development expense (2)													30,792		30,792
Depreciation, amortization and accretion													263,520		263,520
Other expense (3)													210,972		210,972
Income from continuing operations before income taxes															$	219,364
Total assets (4)	$	19,560,579	$	755,290	$	1,195,027	$	4,239,821	$	25,750,717	$	67,226	$	112,251	$	25,930,194

_______________


(1)	Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $0.6 million and $29.3 million, respectively.

(2) Includes $1.7 million of expense previously recorded as segment selling, general, administrative and development expense.

(3) Primarily includes interest expense.

(4) $21.7 million of assets previously recorded to the Asia Property segment have been reclassified to the Other segment.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8981-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9038-108599

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8971-108599

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8595-108599

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8380-108599

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 26
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8844-108599

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8984-108599

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9031-108599

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9054-108599

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8538-108599

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 29
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8864-108599

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8924-108599

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8906-108599

+ Details

SUBSEQUENT EVENTS

3 Months Ended

Mar. 31, 2016

Subsequent Events [Abstract]

SUBSEQUENT EVENTS

Viom Acquisition

On April 21, 2016, the Company acquired a 51% controlling ownership interest in Viom for cash consideration of approximately 76.4 billion INR ($1.1 billion at the date of acquisition) as well as the assumption of approximately 50.6 billion INR ($0.8 billion at the date of acquisition) in existing INR-denominated debt pursuant to its previously announced agreement. The purchase price is subject to post-closing adjustments. The Company borrowed $1.2 billion under the 2013 Credit Facility, which it primarily used, together with cash on hand, to fund the cash portion of the purchase price. The acquisition is consistent with the Company’s strategy to expand in selected geographic areas.

The following table summarizes the preliminary allocation of the purchase price for the Viom Acquisition based upon the estimated fair value at the date of acquisition (in thousands):



Current assets	$	215,060
Non-current assets	61,456
Property and equipment	757,564
Intangible assets (1):
Customer-related intangible assets	1,366,217
Network location intangible assets	640,259
Other intangible assets	10,543
Current liabilities	(189,133		)
Deferred tax liability	(644,262		)
Other non-current liabilities	(86,659		)
Net assets acquired	2,131,045
Goodwill (2)	905,984
Fair value of net assets acquired	3,037,029
Debt assumed	(762,797		)
Preferred stock outstanding	(25,002		)
Non-controlling interest	(1,099,250		)
Purchase Price	$	1,149,980

_______________

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

(2) Goodwill was allocated to the Company’s Asia property segment. The Company expects goodwill will not be deductible for local tax

purposes.

DESCRIPTION OF BUSINESS, BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	American Tower Corporation (together with its subsidiaries, “ATC” or the “Company”) is one of the largest global real estate investment trusts and a leading independent owner, operator and developer of multitenant communications real estate. The Company’s primary business is the leasing of space on 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, which the Company refers to as its property operations. Additionally, the Company offers tower-related services, referred to as its services operations, in the United States, including site acquisition, zoning and permitting and structural analysis, which primarily support its site leasing business, including the addition of new tenants and equipment on its sites. The Company’s portfolio primarily consists of towers it owns and towers it operates pursuant to long-term lease arrangements, as well as distributed antenna system (“DAS”) networks, which provide seamless coverage solutions for in-building and outdoor wireless environments. In addition to the communications sites in its portfolio, the Company manages rooftop and tower sites for property owners under various contractual arrangements. The Company also holds property interests that it leases to communications service providers and third-party tower operators. ATC is a holding company that conducts its operations through its directly and indirectly owned subsidiaries and its joint ventures. ATC’s principal domestic operating subsidiaries are American Towers LLC and SpectraSite Communications, LLC. ATC conducts its international operations primarily through its subsidiary, American Tower International, Inc., which in turn conducts operations through its various international holding and operating subsidiaries and joint ventures. The Company operates as a real estate investment trust for U.S. federal income tax purposes (“REIT”). Accordingly, the Company generally is not subject to U.S. federal income taxes on income generated by its U.S. REIT operations, including the income derived from leasing space on its towers, as the Company receives a dividends paid deduction for distributions to stockholders that generally offsets its income and gains. However, the Company remains obligated to pay U.S. federal income taxes on earnings from its domestic taxable REIT subsidiaries (“TRSs”). In addition, the Company’s international assets and operations, regardless of their designation for U.S. tax purposes, continue to be subject to taxation in the foreign jurisdictions where those assets are held or those operations are conducted. The use of TRSs enables the Company to continue to engage in certain businesses while complying with REIT qualification requirements. The Company may, from time to time, change the election of previously designated TRSs to be included as part of the REIT. As of March 31, 2016, the Company’s U.S. REIT-qualified businesses included its U.S. tower leasing business, most of its operations in Costa Rica, Germany and Mexico and a majority of its services segment and indoor DAS networks business. The accompanying consolidated and condensed consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission. The financial information included herein is unaudited; however, the Company believes that all adjustments 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, 2015 (the “2015 Form 10-K”). The results of operations for the three months ended March 31, 2016 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 or cost method, depending upon the Company’s ability to exercise significant influence over operating and financial policies. All intercompany accounts and transactions have been eliminated.
Accounting Standards Updates	In May 2014, the Financial Accounting Standards Board (the “FASB”) issued new revenue recognition guidance, which requires an entity to recognize revenue in an amount that reflects the consideration to which the entity expects to be entitled in exchange for the transfer of promised goods or services to customers. The standard will replace most existing revenue recognition guidance and will become effective for the Company on January 1, 2018. Early adoption is permitted for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2016. The standard permits the use of either the retrospective or cumulative effect transition method. Leases are not included in the scope of this standard. The Company is evaluating the impact this standard will have on its financial statements. In January 2016, the FASB issued new guidance on the recognition and measurement of financial assets and financial liabilities. The guidance amends certain aspects of recognition, measurement, presentation and disclosure of financial instruments. This standard is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2017. The Company does not expect the adoption of this guidance to have a material effect on the Company’s financial statements. In February 2016, the FASB issued new guidance on the accounting for leases. The guidance amends the existing accounting standards for lease accounting, including the requirement that lessees recognize assets and liabilities for leases with terms greater than twelve months in the statement of financial position. Under the new guidance, lessor accounting is largely unchanged. This guidance is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2018. The Company is evaluating the impact this standard will have on its financial statements. In March 2016, the FASB issued new guidance on the accounting for share-based payment transactions. The guidance amends the accounting for taxes related to stock-based compensation, including how excess tax benefits and a company’s payments for tax withholdings should be classified. This guidance is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2016. The Company does not expect the adoption of this guidance to have a material effect on its financial statements.

PREPAID AND OTHER CURRENT ASSETS (Tables)

3 Months Ended

Mar. 31, 2016

Prepaid Expense and Other Assets, Current [Abstract]

Prepaid and other current assets

Prepaid and other current assets consisted of the following (in thousands):



	As of
	March 31, 2016		December 31, 2015
Prepaid operating ground leases	$	124,450	$	128,542
Prepaid assets	48,553		32,892
Prepaid income tax	44,133		45,056
Unbilled receivables	33,562		34,173
Value added tax and other consumption tax receivables	24,294		30,239
Other miscellaneous current assets	66,799		35,333
Total	$	341,791	$	306,235

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)

3 Months Ended

Mar. 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

Finite intangible assets

The Company’s other intangible assets subject to amortization consisted of the following (in thousands):



		As of March 31, 2016							As of December 31, 2015
	Estimated Useful Lives	Gross Carrying Value		Accumulated Amortization			Net Book Value		Gross Carrying Value		Accumulated Amortization			Net Book Value
	(years)	(in thousands)
Acquired network location intangibles (1)	Up to 20	$	4,019,860	$	(1,109,770	)	$	2,910,090	$	3,980,281	$	(1,052,393	)	$	2,927,888
Acquired customer-related intangibles	15-20	8,747,912		(1,879,003		)	6,868,909		8,640,554		(1,763,853		)	6,876,701
Acquired licenses and other intangibles	3-20	26,213		(1,707		)	24,506		28,293		(5,486		)	22,807
Economic Rights, TV Azteca	70	21,799		(11,314		)	10,485		21,688		(11,208		)	10,480
Total other intangible assets		$	12,815,784	$	(3,001,794	)	$	9,813,990	$	12,670,816	$	(2,832,940	)	$	9,837,876

_______________


(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 (in millions):



Fiscal Year
Remainder of 2016	$	451.4
2017	603.8
2018	602.8
2019	600.4
2020	583.3
2021	574.4

LONG-TERM OBLIGATIONS (Tables)

3 Months Ended

Mar. 31, 2016

Long-term Debt, Excluding Current Maturities [Abstract]

Long-term financing arrangements

Outstanding amounts under the Company’s long-term obligations, reflecting discounts, premiums and debt issuance costs, consisted of the following (in thousands):



	As of
	March 31, 2016			December 31, 2015			Maturity Date
Series 2013-1A securities (1)	$	497,769		$	497,478		March 15, 2018
Series 2013-2A securities (2)	1,289,083			1,288,689			March 15, 2023
Series 2015-1 notes (3)	346,474			346,262			June 15, 2020
Series 2015-2 notes (4)	518,941			518,776			June 16, 2025
2012 GTP notes (5)	279,555			281,902			Various
Unison notes (6)	201,492			201,930			Various
Shareholder loans (7)	145,081			145,540			Various
BR Towers debentures (8)	94,886			85,219			October 15, 2023
Colombian credit facility (9)	60,531			59,640			April 24, 2021
South African facility (10)	52,874			53,175			December 17, 2020
Brazil credit facility (11)	24,021			21,868			January 15, 2022
Indian working capital facility (12)	—			8,752			N/A
Total American Tower subsidiary debt	3,510,707			3,509,231

2013 Credit Facility	31,865			1,225,000			June 28, 2019
Term Loan	1,993,915			1,993,601			January 29, 2021
2014 Credit Facility	1,830,000			1,980,000			January 29, 2021
4.500% senior notes	997,974			997,693			January 15, 2018
3.40% senior notes	999,804			999,769			February 15, 2019
7.25% senior notes	296,502			296,242			May 15, 2019
2.800% senior notes	743,916			743,557			June 1, 2020
5.050% senior notes	697,381			697,216			September 1, 2020
3.300% senior notes	743,900			—			February 15, 2021
3.450% senior notes	643,024			642,786			September 15, 2021
5.900% senior notes	497,307			497,188			November 1, 2021
4.70% senior notes	695,545			695,374			March 15, 2022
3.50% senior notes	988,365			987,966			January 31, 2023
5.00% senior notes	1,003,403			1,003,453			February 15, 2024
4.000% senior notes	739,322			739,057			June 1, 2025
4.400% senior notes	494,911			—			February 15, 2026
Total American Tower Corporation debt	13,397,134			13,498,902
Other debt, including capital lease obligations	114,254			110,876
Total	17,022,095			17,119,009
Less current portion of long-term obligations	(137,853		)	(50,202		)
Long-term obligations	$	16,884,242		$	17,068,807

_______________

(1) Maturity date represents anticipated repayment date; final legal maturity is March 15, 2043.

(2) Maturity date represents anticipated repayment date; final legal maturity is March 15, 2048.

(3) Maturity date represents anticipated repayment date; final legal maturity is June 15, 2045.

(4) Maturity date represents anticipated repayment date; final legal maturity is June 15, 2050.


(5)	Secured debt assumed by the Company in connection with the acquisition of MIP Tower Holdings LLC (“MIPT”). Anticipated repayment dates begin March 15, 2017.


(6)	Secured debt assumed by the Company in connection with the acquisition of certain legal entities from Unison Holdings LLC and Unison Site Management II, L.L.C. Anticipated repayment dates begin April 15, 2017; final legal maturity date is April 15, 2040.


(7)	Reflects balances owed to the Company’s joint venture partners in Ghana and Uganda. The Ghana loan is denominated in Ghanaian Cedi and the Uganda loan is denominated in U.S. Dollars.


(8)	Publicly issued debentures assumed by the Company in connection with the acquisition of BR Towers S.A. Denominated in Brazilian Reais (“BRL”).

(9) Denominated in Colombian Pesos.


(10)	Denominated in South African Rand.

(11) Denominated in BRL.

(12) Denominated in Indian Rupee (“INR”).

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	$	31.9	$	3.2	June 28, 2019 (3)	1.250	%	0.150	%
2014 Credit Facility	$	1,830.0	$	7.4	January 29, 2021 (3)	1.250	%	0.150	%
Term Loan	$	2,000.0	N/A		January 29, 2021	1.250	%	N/A

_______________

(1) LIBOR means the London Interbank Offered Rate.

(2) Fee on undrawn portion of the 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://www.xbrl.org/2003/role/presentationRef
-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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21521-112644

+ Details

FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 2016

Fair Value Disclosures [Abstract]

Schedule of fair value

The fair value of the Company’s financial assets and liabilities that are required to be measured on a recurring basis at fair value was as follows (in thousands):



	March 31, 2016						December 31, 2015
	Fair Value Measurements Using				Assets/Liabilities at Fair Value		Fair Value Measurements Using				Assets/Liabilities at Fair Value
	Level 2		Level 3		Assets/Liabilities at Fair Value		Level 2		Level 3		Assets/Liabilities at Fair Value
Assets:
Interest rate swap agreements	$	790	—		$	790	$	692	—		$	692
Embedded derivative in lease agreement	—		$	13,955	$	13,955	—		$	14,176	$	14,176
Liabilities:
Acquisition-related contingent consideration	—		$	11,816	$	11,816	—		$	12,436	$	12,436

STOCK-BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2016

Share-based Compensation, Allocation and Classification in Financial Statements [Abstract]

Assumptions used to determine the grant date fair value for options granted

Key assumptions used to apply this pricing model were as follows:



Range of risk-free interest rate		1.45% - 1.73%
Weighted average risk-free interest rate		1.45%
Range of expected life of stock options		4.5 - 5.2 years
Range of expected volatility of the underlying stock price		20.64% - 21.45%
Weighted average expected volatility of underlying stock price		21.45%
Range of expected annual dividend yield		1.85% - 2.40%

Summary of the company's option activity

The Company’s option activity for the three months ended March 31, 2016 was as follows:



	Number of Options
Outstanding as of January 1, 2016	7,680,819
Granted	1,132,596
Exercised	(262,877	)
Expired	(500	)
Outstanding as of March 31, 2016	8,550,038

Summary of the company's restricted stock unit activity

The Company’s RSU and PSU activity for the three months ended March 31, 2016 was as follows:



	RSUs		PSUs
Outstanding as of January 1, 2016 (1)	1,656,993		33,377
Granted (2)	765,607		192,719
Vested	(623,111	)	—
Forfeited	(21,573	)	—
Outstanding as of March 31, 2016	1,777,916		226,096

_______________


(1)	PSUs represent the shares issuable for the 2015 PSUs at the end of the three-year performance cycle based on exceeding the performance metric for the first year’s performance period.


(2)	PSUs represent the target number of shares issuable at the end of the three-year performance cycle attributable to the second year’s performance period for the 2015 PSUs and the target number of shares issuable at the end of the three-year performance cycle for the 2016 PSUs.

EARNINGS PER COMMON SHARE (Tables)

3 Months Ended

Mar. 31, 2016

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 (in thousands, except per share data):



	Three Months Ended March 31,
	2016			2015
Net income attributable to American Tower Corporation stockholders	$	275,159		$	193,317
Dividends on preferred stock	(26,781		)	(9,819		)
Net income attributable to American Tower Corporation common stockholders	248,378			183,498
Basic weighted average common shares outstanding	424,059			405,111
Dilutive securities	3,829			4,288
Diluted weighted average common shares outstanding	427,888			409,399
Basic net income attributable to American Tower Corporation common stockholders per common share	$	0.59		$	0.45
Diluted net income attributable to American Tower Corporation common stockholders per common share	$	0.58		$	0.45

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 March 31,
	2016	2015
Restricted stock awards	152	3
Stock options	2,322	501
Preferred stock	17,413	9,194

ACQUISITIONS (Tables)

3 Months Ended

Mar. 31, 2016

Business Combination, Description [Abstract]

Schedule of merger and acquisition related costs

The Company recorded acquisition and merger related expenses and integration costs as follows (in thousands):



	Three Months Ended March 31,
	2016		2015
Acquisition and merger related expenses	$	985	$	2,966
Integration costs	$	3,271	$	1,755

Schedule of pro forma information



	Three Months Ended March 31, 2015
Pro forma revenues	$	1,263,174
Pro forma net income attributable to American Tower Corporation common stockholders	$	150,024
Pro forma net income per common share amounts:
Basic net income attributable to American Tower Corporation common stockholders	$	0.35
Diluted net income attributable to American Tower Corporation common stockholders	$	0.35

BUSINESS SEGMENTS (Tables)

3 Months Ended

Mar. 31, 2016

Segment Reporting, Measurement Disclosures [Abstract]

Summarized financial information concerning the company's reportable segments



	Property								Total Property		Services		Other		Total
Three Months Ended March 31, 2016	U.S.		Asia		EMEA		Latin America		Total Property		Services		Other		Total
	(in thousands)
Segment revenues	$	851,744	$	63,216	$	129,640	$	223,051	$	1,267,651	$	21,396			$	1,289,047
Segment operating expenses (1)	177,722		33,080		55,659		75,322		341,783		9,004				350,787
Interest income, TV Azteca, net	—		—		—		2,716		2,716		—				2,716
Segment gross margin	674,022		30,136		73,981		150,445		928,584		12,392				940,976
Segment selling, general, administrative and development expense (1)	37,286		6,576		16,152		14,584		74,598		2,916				77,514
Segment operating profit	$	636,736	$	23,560	$	57,829	$	135,861	$	853,986	$	9,476			$	863,462
Stock-based compensation expense													$	28,079	28,079
Other selling, general, administrative and development expense													30,380		30,380
Depreciation, amortization and accretion													341,634		341,634
Other expense (2)													152,938		152,938
Income from continuing operations before income taxes															$	310,431
Total assets	$	19,110,950	$	698,798	$	2,327,461	$	4,668,298	$	26,805,507	$	61,117	$	197,691	$	27,064,315

_______________


(1)	Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $0.7 million and $27.4 million, respectively.


(2)	Primarily includes interest expense.



	Property								Total Property		Services		Other		Total
Three Months Ended March 31, 2015	U.S.		Asia		EMEA		Latin America		Total Property		Services		Other		Total
	(in thousands)
Segment revenues	$	717,880	$	57,127	$	75,801	$	211,372	$	1,062,180	$	17,010			$	1,079,190
Segment operating expenses (1)	133,032		29,660		28,515		67,618		258,825		5,244				264,069
Interest income, TV Azteca, net	—		—		—		2,596		2,596		—				2,596
Segment gross margin	584,848		27,467		47,286		146,350		805,951		11,766				817,717
Segment selling, general, administrative and development expense (1)	26,822		6,829		8,859		17,262		59,772		3,436				63,208
Segment operating profit	$	558,026	$	20,638	$	38,427	$	129,088	$	746,179	$	8,330			$	754,509
Stock-based compensation expense													$	29,861	29,861
Other selling, general, administrative and development expense (2)													30,792		30,792
Depreciation, amortization and accretion													263,520		263,520
Other expense (3)													210,972		210,972
Income from continuing operations before income taxes															$	219,364
Total assets (4)	$	19,560,579	$	755,290	$	1,195,027	$	4,239,821	$	25,750,717	$	67,226	$	112,251	$	25,930,194

_______________


(1)	Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $0.6 million and $29.3 million, respectively.

(2) Includes $1.7 million of expense previously recorded as segment selling, general, administrative and development expense.

(3) Primarily includes interest expense.

(4) $21.7 million of assets previously recorded to the Asia Property segment have been reclassified to the Other segment.

SUBSEQUENT EVENTS (Tables)

3 Months Ended

Mar. 31, 2016

Subsequent Events [Abstract]

Schedule of preliminary allocation of the purchase price

The following table summarizes the preliminary allocation of the purchase price for the Viom Acquisition based upon the estimated fair value at the date of acquisition (in thousands):



Current assets	$	215,060
Non-current assets	61,456
Property and equipment	757,564
Intangible assets (1):
Customer-related intangible assets	1,366,217
Network location intangible assets	640,259
Other intangible assets	10,543
Current liabilities	(189,133		)
Deferred tax liability	(644,262		)
Other non-current liabilities	(86,659		)
Net assets acquired	2,131,045
Goodwill (2)	905,984
Fair value of net assets acquired	3,037,029
Debt assumed	(762,797		)
Preferred stock outstanding	(25,002		)
Non-controlling interest	(1,099,250		)
Purchase Price	$	1,149,980

_______________

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

(2) Goodwill was allocated to the Company’s Asia property segment. The Company expects goodwill will not be deductible for local tax

purposes.

PREPAID AND OTHER CURRENT ASSETS (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid operating ground leases	$ 124,450	$ 128,542
Prepaid assets	48,553	32,892
Prepaid income tax	44,133	45,056
Unbilled receivables	33,562	34,173
Value added tax and other consumption tax receivables	24,294	30,239
Other miscellaneous current assets	66,799	35,333
Total	$ 341,791	$ 306,235

GOODWILL AND OTHER INTANGIBLE ASSETS - CHANGES IN THE CARRYING VALUE OF GOODWILL (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 12,815,784	$ 12,670,816
Accumulated Amortization	(3,001,794)	(2,832,940)
Net Book Value	9,813,990	9,837,876
Acquired Network Location
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	4,019,860	3,980,281
Accumulated Amortization	(1,109,770)	(1,052,393)
Net Book Value	$ 2,910,090	2,927,888
Acquired Network Location \| Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	0 years
Acquired Network Location \| Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	20 years
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 8,747,912	8,640,554
Accumulated Amortization	(1,879,003)	(1,763,853)
Net Book Value	$ 6,868,909	6,876,701
Customer Relationships \| Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	15 years
Customer Relationships \| Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	20 years
Acquired Licenses And Other Intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 26,213	28,293
Accumulated Amortization	(1,707)	(5,486)
Net Book Value	$ 24,506	22,807
Acquired Licenses And Other Intangibles \| Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	3 years
Acquired Licenses And Other Intangibles \| Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	20 years
Economic Rights, TV Azteca
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 21,799	21,688
Accumulated Amortization	(11,314)	(11,208)
Net Book Value	$ 10,485	$ 10,480
Finite-lived intangible asset, useful life	70 years

GOODWILL AND OTHER INTANGIBLE ASSETS - EXPECTED FUTURE AMORTIZATION EXPENSE (Details) $ in Millions	Mar. 31, 2016 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2016	$ 451.4
2017	603.8
2018	602.8
2019	600.4
2020	583.3
2021	$ 574.4

GOODWILL AND OTHER INTANGIBLE ASSETS - NARRATIVE (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 151,800	$ 110,500
Weighted Average
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, remaining amortization period	16 years
Non-US
Acquired Finite-Lived Intangible Assets [Line Items]
Effect of foreign currency translation	$ 31,596

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Accrued Liabilities, Current [Abstract]
Accrued property and real estate taxes	$ 81,799	$ 75,827
Accrued rent	42,229	54,732
Payroll and related withholdings	39,965	62,334
Accrued construction costs	14,120	19,857
Other accrued expenses	259,433	303,663
Total	$ 437,546	$ 516,413

LONG-TERM OBLIGATIONS - LONG-TERM FINANCING ARRANGEMENTS (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Jan. 12, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Other debt, including capital lease obligations	$ 114,254		$ 110,876
Debt, long-term and short-term, combined amount	17,022,095		17,119,009
Less current portion long-term obligations	(137,853)		(50,202)
Long-term debt, excluding current maturities	16,884,242		17,068,807
Subsidiaries
Debt Instrument [Line Items]
Long-term debt	3,510,707		3,509,231
Parent
Debt Instrument [Line Items]
Long-term debt	13,397,134		13,498,902
Secured Cellular Site Revenue Notes
Debt Instrument [Line Items]
Less current portion long-term obligations	(97,700)
South African Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt	52,874		53,175
Brazil Credit Facility
Debt Instrument [Line Items]
Long-term debt	24,021		21,868
Indian Facility
Debt Instrument [Line Items]
Long-term debt	0		8,752
Credit Facility 2013 \| Revolving Credit Facility
Debt Instrument [Line Items]
Long-term Line of Credit	31,865		1,225,000
Credit Facility 2014 \| Revolving Credit Facility
Debt Instrument [Line Items]
Long-term Line of Credit	1,830,000		1,980,000
Secured Debt \| Commercial Mortgage Pass Through Certificates Series 2013 \| Secured Tower Revenue Securities, Series 2013-1A
Debt Instrument [Line Items]
Long-term debt	497,769		497,478
Secured Debt \| Commercial Mortgage Pass Through Certificates Series 2013 \| Secured Tower Revenue Securities, Series 2013-2A
Debt Instrument [Line Items]
Long-term debt	1,289,083		1,288,689
Secured Debt \| Series 2015-1 Class A
Debt Instrument [Line Items]
Long-term debt	346,474		346,262
Secured Debt \| Series 2015-2 Class A
Debt Instrument [Line Items]
Long-term debt	518,941		518,776
Secured Debt \| GTP Notes
Debt Instrument [Line Items]
Long-term debt	279,555		281,902
Secured Debt \| Secured Cellular Site Revenue Notes
Debt Instrument [Line Items]
Long-term debt	201,492		201,930
Secured Debt \| BR Towers Debentures
Debt Instrument [Line Items]
Long-term debt	94,886		85,219
Unsecured Debt \| Shareholder Loans
Debt Instrument [Line Items]
Long-term debt	145,081		145,540
Unsecured Debt \| Term Loan 2013
Debt Instrument [Line Items]
Long-term debt	1,993,915		1,993,601
Revolving Credit Facility \| Colombian Long Term Credit Facility
Debt Instrument [Line Items]
Long-term debt	60,531		59,640
Senior Notes \| 4.50% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 997,974		$ 997,693
Long-term debt, stated interest rate	4.50%		4.50%
Senior Notes \| 3.40% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 999,804		$ 999,769
Long-term debt, stated interest rate	3.40%		3.40%
Senior Notes \| 7.25% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 296,502		$ 296,242
Long-term debt, stated interest rate	7.25%		7.25%
Senior Notes \| 2.80% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 743,916		$ 743,557
Long-term debt, stated interest rate	2.80%		2.80%
Senior Notes \| 5.05% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 697,381		$ 697,216
Long-term debt, stated interest rate	5.05%		5.05%
Senior Notes \| 3.30% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 743,900		$ 0
Long-term debt, stated interest rate	3.30%	3.30%	3.30%
Senior Notes \| 3.450% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 643,024		$ 642,786
Long-term debt, stated interest rate	3.45%		3.45%
Senior Notes \| 5.90% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 497,307		$ 497,188
Long-term debt, stated interest rate	5.90%		5.90%
Senior Notes \| 4.70% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 695,545		$ 695,374
Long-term debt, stated interest rate	4.70%		4.70%
Senior Notes \| 3.50% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 988,365		$ 987,966
Long-term debt, stated interest rate	3.50%		3.50%
Senior Notes \| 5.00% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 1,003,403		$ 1,003,453
Long-term debt, stated interest rate	5.00%		5.00%
Senior Notes \| 4.00% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 739,322		$ 739,057
Long-term debt, stated interest rate	4.00%		4.00%
Senior Notes \| 4.40% Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 494,911		$ 0
Long-term debt, stated interest rate	4.40%	4.40%	4.40%

LONG-TERM OBLIGATIONS - SCHEDULE OF LINES OF CREDIT (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Credit Facility 2013 \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Letters of credit, amount outstanding	$ 3.2
Line of credit facility, commitment fee percentage	0.15%
Credit Facility 2013 \| Unsecured Debt
Line of Credit Facility [Line Items]
Principal amount	$ 31.9
Credit Facility 2013 \| Unsecured Debt \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.25%
Credit Facility 2014 \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Letters of credit, amount outstanding	$ 7.4
Line of credit facility, commitment fee percentage	0.15%
Credit Facility 2014 \| Unsecured Debt
Line of Credit Facility [Line Items]
Principal amount	$ 1,830.0
Credit Facility 2014 \| Unsecured Debt \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.25%
Term Loan 2013 \| Unsecured Debt
Line of Credit Facility [Line Items]
Principal amount	$ 2,000.0
Term Loan 2013 \| Unsecured Debt \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.25%

LONG-TERM OBLIGATIONS - NARRATIVE (Details) $ in Thousands, € in Millions		3 Months Ended
	Jan. 12, 2016 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2016 EUR (€)	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Current portion of long-term obligations		$ 137,853			$ 50,202
Borrowings under credit facilities		31,504		$ 3,150,000
Secured Cellular Site Revenue Notes
Debt Instrument [Line Items]
Current portion of long-term obligations		97,700
Credit Facility 2013 \| Revolving Credit Facility
Debt Instrument [Line Items]
Borrowings under credit facilities		31,500	€ 28.0
Repayment of indebtedness under credit facility		1,200,000
Credit Facility 2014 \| Revolving Credit Facility
Debt Instrument [Line Items]
Repayment of indebtedness under credit facility		$ 150,000
Senior Notes
Debt Instrument [Line Items]
Maximum Adjusted EBITDA		3.5
Senior Notes \| 3.30% Senior Notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate	3.30%	3.30%			3.30%
Principal amount	$ 750,000
Senior Notes \| 4.40% Senior Notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate	4.40%	4.40%			4.40%
Principal amount	$ 500,000
Senior Notes \| 3.30% and 4.40% Senior Notes
Debt Instrument [Line Items]
Proceeds from the issuance of debt	$ 1,237,200
Senior Notes \| Senior Notes
Debt Instrument [Line Items]
Redemption price, percent		100.00%	100.00%
Conditional repurchase price as percent of principal		101.00%

FAIR VALUE MEASUREMENTS - ASSETS AND LIABILITIES MEASURED AT FAIR VALUE ON A RECURRING BASIS (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Embedded derivative in lease agreement	$ 13,955	$ 14,176
Acquisition-related contingent consideration	11,816	12,436
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Embedded derivative in lease agreement	13,955	14,176
Acquisition-related contingent consideration	11,816	12,436
Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements	790	692
Interest Rate Swap [Member] \| Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements	$ 790	$ 692

FAIR VALUE MEASUREMENTS - NARRATIVE (Details) - USD ($)	Mar. 31, 2016	Dec. 31, 2015
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	25,700,000
Debt, long-term and short-term, combined amount	17,022,095,000	$ 17,119,009,000
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	17,600,000,000	17,400,000,000
Estimate of Fair Value Measurement \| Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	10,100,000,000	8,700,000,000
Estimate of Fair Value Measurement \| Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 7,500,000,000	$ 8,700,000,000

INCOME TAXES - NARRATIVE (Details) - USD ($)	3 Months Ended
INCOME TAXES - NARRATIVE (Details) - USD ($)	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Income Tax Contingency [Line Items]
Unrecognized tax benefits, increase resulting from prior period tax positions	$ 6,500,000
Unrecognized tax benefits, increase resulting from foreign currency fluctuations	900,000
Unrecognized tax benefits, income tax penalties and interest	3,200,000	$ 900,000
Unrecognized tax benefits, income tax penalties and interest accrued	23,800,000		$ 20,200,000
Minimum
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefits is reasonably possible	0
Maximum
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefits is reasonably possible	14,500,000
Other Noncurrent Liabilities
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact the ETR	$ 35,500,000		$ 28,100,000

STOCK-BASED COMPENSATION - ASSUMPTIONS USED TO DETERMINE THE GRANT DATE FAIR VALUE FOR OPTIONS GRANTED (Details) - Employee Stock Option	3 Months Ended
	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum range of risk-free interest rate	1.45%
Maximum range of risk-free interest rate	1.73%
Weighted average risk-free interest rate	1.45%
Minimum range of expected volatility of underlying stock price	20.64%
Maximum range of expected volatility of underlying stock price	21.45%
Weighted average expected volatility of underlying stock price	21.45%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of expected life of stock options	4 years 6 months
Range of expected annual dividend yield	1.85%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of expected life of stock options	5 years 2 months 15 days
Range of expected annual dividend yield	2.40%

STOCK-BASED COMPENSATION - SUMMARY OF THE COMPANY'S OPTION ACTIVITY (Details) - Employee Stock Option	3 Months Ended
	Mar. 31, 2016 shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding as of January 1, 2016	7,680,819
Granted	1,132,596
Exercised	(262,877)
Expired	(500)
Outstanding as of March 31, 2016	8,550,038

STOCK-BASED COMPENSATION - SUMMARY OF THE COMPANY'S RESTRICTED STOCK UNIT ACTIVITY (Details) - shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2016
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Outstanding as of January 1, 2016	1,656,993
Granted	765,607
Vested	(623,111)
Forfeited	(21,573)
Outstanding as of March 31, 2016	1,656,993	1,777,916
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Outstanding as of January 1, 2016	33,377
Granted	192,719
Vested	0
Forfeited	0
Outstanding as of March 31, 2016	33,377	226,096

STOCK-BASED COMPENSATION - NARRATIVE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 28,079	$ 29,861
Capitalized stock-based compensation expense	$ 700	$ 500
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Stock-based compensation expense	$ 800
Total unrecognized compensation expense	$ 18,900
Expected recognition of stock award compensation expense weighted average period in years	2 years
Three year performance grant, shares granted	169,340	70,135
Shares granted, grant date fair value not yet established	23,377
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]
Weighted average grant date fair value (in dollars per share)	$ 14.56
Total unrecognized compensation expense	$ 39,800
Expected recognition of stock award compensation expense weighted average period in years	3 years
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense	$ 120,700
Expected recognition of stock award compensation expense weighted average period in years	3 years
2007 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issuable under stock incentive plan	9,390,000
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]
Vesting period	4 years
Expiration period	10 years
2007 Plan \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years

EQUITY - DISTRIBUTIONS (Detail) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended
	Mar. 09, 2016	Jan. 14, 2016	Dec. 03, 2015	Mar. 31, 2016	Mar. 31, 2015
Dividends Payable [Line Items]
DISTRIBUTIONS DECLARED PER COMMON SHARE				$ 0.51	$ 0.42
Distributions paid on common stock				$ 209,984	$ 152,037
Distributions paid on preferred stock				$ 26,781	$ 7,875
Common Stock
Dividends Payable [Line Items]
DISTRIBUTIONS DECLARED PER COMMON SHARE	$ 0.51		$ 0.49
Distributions paid on common stock	$ 216,500		$ 207,700
Convertible Preferred Stock Subject to Mandatory Redemption \| Series A Preferred Stock
Dividends Payable [Line Items]
Preferred stock, dividends per share, declared		$ 1.3125
Distributions paid on preferred stock		$ 7,900
Convertible Preferred Stock Subject to Mandatory Redemption \| Series B Preferred Stock
Dividends Payable [Line Items]
Preferred stock, dividends per share, declared		$ 13.75
Distributions paid on preferred stock		$ 18,900

EQUITY - NARRATIVE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Class of Stock [Line Items]
Accrued dividend RSU	$ 3,900
Proceeds from stock options	14,582	$ 5,106
Dividends Declared and Paid
Class of Stock [Line Items]
Paid dividend RSU	$ 2,300
Series B Preferred Stock
Class of Stock [Line Items]
Depository shares, percentage of preferred shares	0.1
Convertible Preferred Stock Subject to Mandatory Redemption \| Series A Preferred Stock \| Minimum
Class of Stock [Line Items]
Conversion factor, preferred stock	0.9174
Convertible Preferred Stock Subject to Mandatory Redemption \| Series A Preferred Stock \| Maximum
Class of Stock [Line Items]
Conversion factor, preferred stock	1.1468
Convertible Preferred Stock Subject to Mandatory Redemption \| Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, liquidation preference per share	$ 1,000.00
Shares issued, price per share	$ 100.00
Convertible Preferred Stock Subject to Mandatory Redemption \| Series B Preferred Stock \| Minimum
Class of Stock [Line Items]
Conversion factor, preferred stock	8.5911
Convertible Preferred Stock Subject to Mandatory Redemption \| Series B Preferred Stock \| Maximum
Class of Stock [Line Items]
Conversion factor, preferred stock	10.3093
Preferred Stock \| Convertible Preferred Stock Subject to Mandatory Redemption
Class of Stock [Line Items]
Preferred stock, par value	$ 0.01		$ 0.01
Preferred Stock \| Convertible Preferred Stock Subject to Mandatory Redemption \| Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares issued	6,000,000		6,000,000
Preferred stock, dividend rate percentage (in percent)	5.25%		5.25%
Preferred stock, par value	$ 0.01
Preferred stock, liquidation preference per share	$ 100.00
Preferred Stock \| Convertible Preferred Stock Subject to Mandatory Redemption \| Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares issued	1,375,000		1,375,000
Preferred stock, dividend rate percentage (in percent)	5.50%		5.50%
Preferred stock, par value	$ 0.01
Depository shares, amount issued	13,750,000

EARNINGS PER COMMON SHARE - SCHEDULE OF EARNINGS PER BASIC AND DILUTED BY COMMON CLASS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Net income attributable to American Tower Corporation stockholders	$ 275,159	$ 193,317
Dividends on preferred stock	(26,781)	(9,819)
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION COMMON STOCKHOLDERS	$ 248,378	$ 183,498
Basic weighted average common shares outstanding	424,059	405,111
Dilutive securities	3,829	4,288
Diluted weighted average common shares outstanding	427,888	409,399
Basic net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 0.59	$ 0.45
Diluted net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 0.58	$ 0.45

EARNINGS PER COMMON SHARE - SCHEDULE OF SHARES EXCLUDED FROM COMPUTATION OF EARNINGS PER SHARE (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares issuable upon conversion of the stock-based awards and convertible notes	152	3
Equity Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares issuable upon conversion of the stock-based awards and convertible notes	2,322	501
Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares issuable upon conversion of the stock-based awards and convertible notes	17,413	9,194

COMMITMENTS AND CONTINGENCIES - NARRATIVE (Details)		1 Months Ended	3 Months Ended
COMMITMENTS AND CONTINGENCIES - NARRATIVE (Details)	Mar. 27, 2015 USD ($) communications_site renewal_period	Dec. 31, 2000 USD ($) tower	Mar. 31, 2016 USD ($) tower renewal_period shares
Verizon Transaction
Loss Contingencies [Line Items]
Capital leased assets, number of units \| communications_site	11,286
Right to lease, weighted average term	28 years
Aggregate purchase option price for towers \| $	$ 5,000,000,000
Customer lease, initial term	10 years
Successive terms to renew lease \| renewal_period	8
Renewal term	5 years
AT&T Transaction
Loss Contingencies [Line Items]
Capital leased assets, number of units \| tower			2,370
Aggregate purchase option price for towers \| $			$ 713,400,000
Successive terms to renew lease \| renewal_period			4
Operating lease, term of contract			27 years
Number of communications sites acquired \| tower			60
Purchase price accretion rate (per year)			10.00%
AT&T Transaction \| Commitments prior to June 30, 2020
Loss Contingencies [Line Items]
Renewal term			5 years
AT&T Transaction \| Commitments subsequent to June 30, 2020
Loss Contingencies [Line Items]
Renewal term			1 year
ALLTEL Transaction
Loss Contingencies [Line Items]
Capital leased assets, number of units \| tower		1,800
Aggregate purchase option price for towers \| $			$ 75,800,000
Number of communications sites acquired \| tower			1,525
Purchase price accretion rate (per year)		3.00%
Average lease term (in years)		15 years
Cash purchase price per tower \| $		$ 27,500
Purchase price of tower in shares of common stock \| shares			769

ACQUISITIONS - PRO FORMA INFORMATION (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2015 USD ($) $ / shares
Business Acquisition, Pro Forma Information [Abstract]
Pro forma operating revenues \| $	$ 1,263,174
Pro forma net income attributable to American Tower Corporation \| $	$ 150,024
Basic net income attributable to American Tower Corporation common stockholders (in dollars per share) \| $ / shares	$ 0.35
Diluted net income attributable to American Tower Corporation common stockholders (in dollars per share) \| $ / shares	$ 0.35

ACQUISITIONS - NARRATIVE (Details) $ in Thousands, ₨ in Billions				3 Months Ended
	Apr. 21, 2016 USD ($) site system	Apr. 21, 2016 INR (₨) site system	Mar. 17, 2016 USD ($) site	Mar. 31, 2016 USD ($) site communications_site	Mar. 31, 2015 USD ($)
Business Acquisition [Line Items]
Acquisition and merger related expenses \| $				$ 985	$ 2,966
Integration costs \| $				$ 3,271	$ 1,755
Verizon Transaction
Business Acquisition [Line Items]
Number of communications sites acquired				11,500
Airtel Acquisition
Business Acquisition [Line Items]
Number of communications sites acquired \| communications_site				4,700
TIM Acquisition
Business Acquisition [Line Items]
Number of communications sites acquired \| communications_site				5,500
Viom Transaction
Business Acquisition [Line Items]
Number of communications sites acquired	42,000	42,000
Distributed antenna systems acquired \| system	200	200
Viom Transaction \| Subsequent Event
Business Acquisition [Line Items]
Percentage of voting interest acquired	51.00%	51.00%
Aggregate purchase price	$ 1,100,000	₨ 76.4
Airtel Tanzania
Business Acquisition [Line Items]
Number of communications sites acquired			1,350
Airtel Tanzania \| Preliminary Purchase Price Allocation
Business Acquisition [Line Items]
Aggregate purchase price \| $			$ 179,000
Additional sites to be acquired			100

BUSINESS SEGMENTS - SUMMARIZED FINANCIAL INFORMATION CONCERNING THE COMPANY'S REPORTABLE SEGMENTS (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2016 USD ($) segment	Mar. 31, 2015 USD ($)	Sep. 30, 2015 segment	Dec. 31, 2015 USD ($)
Segment Reporting, Measurement Disclosures [Abstract]
Number of reportable segments \| segment	5		3
Segment Reporting Information [Line Items]
Segment revenues	$ 1,289,047	$ 1,079,190
Segment operating expenses	350,787	264,069
Segment gross margin	940,976	817,717
Segment selling, general, administrative and development expense	77,514	63,208
Segment operating profit	863,462	754,509
Stock-based compensation expense	28,079	29,861
Other selling, general, administrative and development expense	30,380	30,792
Depreciation, amortization and accretion	341,634	263,520
Other expense (2)	152,938	210,972
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	310,431	219,364
Total assets	27,064,315	25,930,194		$ 26,904,272
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Stock-based compensation expense	28,079	29,861
Other selling, general, administrative and development expense	30,380	30,792
Depreciation, amortization and accretion	341,634	263,520
Other expense (2)	152,938	210,972
Total assets	197,691	112,251
Amount previously recorded as segment selling, general and administrative expense		1,700
Corporate, Non-Segment \| Restatement Adjustment
Segment Reporting Information [Line Items]
Total assets		21,700
Operating Expense
Segment Reporting Information [Line Items]
Stock-based compensation expense	700	600
Operating Segments \| Network Development Services
Segment Reporting Information [Line Items]
Segment revenues	21,396	17,010
Segment operating expenses	9,004	5,244
Segment gross margin	12,392	11,766
Segment selling, general, administrative and development expense	2,916	3,436
Segment operating profit	9,476	8,330
Total assets	61,117	67,226
Operating Segments \| Property
Segment Reporting Information [Line Items]
Segment revenues	1,267,651	1,062,180
Segment operating expenses	341,783	258,825
Segment gross margin	928,584	805,951
Segment selling, general, administrative and development expense	74,598	59,772
Segment operating profit	853,986	746,179
Total assets	26,805,507	25,750,717
Operating Segments \| Property \| United States
Segment Reporting Information [Line Items]
Segment revenues	851,744	717,880
Segment operating expenses	177,722	133,032
Segment gross margin	674,022	584,848
Segment selling, general, administrative and development expense	37,286	26,822
Segment operating profit	636,736	558,026
Total assets	19,110,950	19,560,579
Operating Segments \| Property \| Asia
Segment Reporting Information [Line Items]
Segment revenues	63,216	57,127
Segment operating expenses	33,080	29,660
Segment gross margin	30,136	27,467
Segment selling, general, administrative and development expense	6,576	6,829
Segment operating profit	23,560	20,638
Total assets	698,798	755,290
Operating Segments \| Property \| EMEA
Segment Reporting Information [Line Items]
Segment revenues	129,640	75,801
Segment operating expenses	55,659	28,515
Segment gross margin	73,981	47,286
Segment selling, general, administrative and development expense	16,152	8,859
Segment operating profit	57,829	38,427
Total assets	2,327,461	1,195,027
Operating Segments \| Property \| Latin America
Segment Reporting Information [Line Items]
Segment revenues	223,051	211,372
Segment operating expenses	75,322	67,618
Segment gross margin	150,445	146,350
Segment selling, general, administrative and development expense	14,584	17,262
Segment operating profit	135,861	129,088
Total assets	4,668,298	4,239,821
Selling General Administrative And Development Expense
Segment Reporting Information [Line Items]
Stock-based compensation expense	27,421	29,290
TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net of interest expense of $283 and $370, respectively	2,716	2,596
TV Azteca \| Operating Segments \| Network Development Services
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net of interest expense of $283 and $370, respectively	0	0
TV Azteca \| Operating Segments \| Property
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net of interest expense of $283 and $370, respectively	2,716	2,596
TV Azteca \| Operating Segments \| Property \| United States
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net of interest expense of $283 and $370, respectively	0	0
TV Azteca \| Operating Segments \| Property \| Asia
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net of interest expense of $283 and $370, respectively	0	0
TV Azteca \| Operating Segments \| Property \| EMEA
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net of interest expense of $283 and $370, respectively	0	0
TV Azteca \| Operating Segments \| Property \| Latin America
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net of interest expense of $283 and $370, respectively	$ 2,716	$ 2,596

SUBSEQUENT EVENTS (Details) $ in Thousands, ₨ in Billions	Apr. 21, 2016 USD ($)	Apr. 21, 2016 INR (₨)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Subsequent Event [Line Items]
GOODWILL			$ 4,123,401	$ 4,091,805
Subsequent Event \| Viom Transaction
Subsequent Event [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets	$ 215,060
Non-current assets	61,456
Property and equipment	757,564
Current liabilities	(189,133)
Deferred tax liability	(644,262)
Other non-current liabilities	(86,659)
Net assets acquired	2,131,045
GOODWILL	905,984
Fair value of net assets acquired	3,037,029
Debt assumed	(762,797)	₨ (50.6)
Preferred stock outstanding	(25,002)
Non-controlling interest	(1,099,250)
Purchase Price	1,100,000	₨ 76.4
Subsequent Event \| Viom Transaction \| Customer Relationships
Subsequent Event [Line Items]
Intangible assets acquired	1,366,217
Subsequent Event \| Viom Transaction \| Acquired Network Location
Subsequent Event [Line Items]
Intangible assets acquired	640,259
Subsequent Event \| Viom Transaction \| Other Intangible Assets
Subsequent Event [Line Items]
Intangible assets acquired	$ 10,543

SUBSEQUENT EVENTS - NARRATIVE (Details) $ in Thousands, ₨ in Billions			1 Months Ended	3 Months Ended
	Apr. 21, 2016 USD ($)	Apr. 21, 2016 INR (₨)	Apr. 29, 2016 USD ($)	Mar. 31, 2016
Acquired Network Location \| Maximum
Subsequent Event [Line Items]
Finite-lived intangible asset, useful life				20 years
Subsequent Event \| Viom Transaction
Subsequent Event [Line Items]
Percentage of voting interest acquired	51.00%	51.00%
Purchase Price	$ 1,100,000	₨ 76.4
Fair value of debt assumed through acquisitions	$ 762,797	₨ 50.6
Revolving Credit Facility \| Credit Facility 2013 \| Subsequent Event
Subsequent Event [Line Items]
Proceeds from the issuance of debt			$ 1,200,000

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Cash Flows [Abstract]
Income tax refunds	$ 3,431	$ 922