Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2016	Jul. 21, 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	Jun. 30, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		425,489,212

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
CURRENT ASSETS:
Cash and cash equivalents	$ 410,538	$ 320,686
Restricted cash	142,761	142,193
Accounts receivable, net	285,422	227,354
Prepaid and other current assets	481,879	306,235
Total current assets	1,320,600	996,468
PROPERTY AND EQUIPMENT, net	10,575,425	9,866,424
GOODWILL	4,981,919	4,091,805
OTHER INTANGIBLE ASSETS, net	11,590,692	9,837,876
DEFERRED INCOME TAXES	229,273	212,041
DEFERRED RENT ASSET	1,233,002	1,166,755
NOTES RECEIVABLE AND OTHER NON-CURRENT ASSETS	809,287	732,903
TOTAL	30,740,198	26,904,272
CURRENT LIABILITIES:
Accounts payable	120,586	96,714
Accrued expenses	617,711	516,413
Distributions payable	227,594	210,027
Accrued interest	151,365	115,672
Current portion of long-term obligations	314,063	50,202
Unearned revenue	224,312	211,001
Total current liabilities	1,655,631	1,200,029
LONG-TERM OBLIGATIONS	18,403,013	17,068,807
ASSET RETIREMENT OBLIGATIONS	951,803	856,936
DEFERRED TAX LIABILITY	745,936	106,333
OTHER NON-CURRENT LIABILITIES	1,058,433	959,349
Total liabilities	22,814,816	20,191,454
COMMITMENTS AND CONTINGENCIES
REDEEMABLE NONCONTROLLING INTERESTS	1,085,157	0
EQUITY:
Common stock: $.01 par value; 1,000,000,000 shares authorized; 428,071,284 and 426,695,279 shares issued; and 425,261,258 and 423,885,253 shares outstanding, respectively	4,280	4,267
Additional paid-in capital	9,781,223	9,690,609
Distributions in excess of earnings	(1,033,324)	(998,535)
Accumulated other comprehensive loss	(1,770,998)	(1,836,996)
Treasury stock (2,810,026 shares at cost)	(207,740)	(207,740)
Total American Tower Corporation equity	6,773,515	6,651,679
Noncontrolling interests	66,710	61,139
Total equity	6,840,225	6,712,818
TOTAL	30,740,198	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
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

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	6 Months Ended	12 Months Ended
CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	Jun. 30, 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	428,071,284	426,695,279
Common stock, shares outstanding	425,261,258	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, dividend rate percentage (in percent)	5.25%	5.25%
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 (in dollars)	$ 600,000	$ 600,000
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, dividend rate percentage (in percent)	5.50%	5.50%
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 (in dollars)	$ 1,375,000	$ 1,375,000

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
REVENUES:
Property	$ 1,426,192	$ 1,154,235	$ 2,693,843	$ 2,216,415
Services	16,035	20,140	37,431	37,150
Total operating revenues	1,442,227	1,174,375	2,731,274	2,253,565
OPERATING EXPENSES:
Property (including stock-based compensation expense of $392, $390, $899 and $822, respectively)	452,571	314,285	794,861	573,542
Services (including stock-based compensation expense of $255, $98, $406 and $237, respectively)	7,140	8,173	16,295	13,556
Depreciation, amortization and accretion	397,765	328,356	739,399	591,876
Selling, general, administrative and development expense (including stock-based compensation expense of $21,260, $23,557, $48,681 and $52,847, respectively)	138,234	116,338	273,549	239,628
Other operating expenses	13,711	17,449	22,511	25,223
Total operating expenses	1,009,421	784,601	1,846,615	1,443,825
OPERATING INCOME	432,806	389,774	884,659	809,740
OTHER INCOME (EXPENSE):
Gain (loss) on retirement of long-term obligations	830	(75,068)	830	(78,793)
Other expense (including unrealized foreign currency (losses) gains of ($24,585), $25,461, $4,777 and ($30,007), respectively)	(25,842)	(2,129)	(13,634)	(56,632)
Total other expense	(196,832)	(218,638)	(338,254)	(419,240)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	235,974	171,136	546,405	390,500
Income tax provision	(43,510)	(13,956)	(72,634)	(37,828)
NET INCOME	192,464	157,180	473,771	352,672
Net income attributable to noncontrolling interests	(4,914)	(1,124)	(11,062)	(3,299)
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION STOCKHOLDERS	187,550	156,056	462,709	349,373
Dividends on preferred stock	(26,782)	(26,782)	(53,563)	(36,601)
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION COMMON STOCKHOLDERS	$ 160,768	$ 129,274	$ 409,146	$ 312,772
NET INCOME PER COMMON SHARE AMOUNTS:
Basic net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 0.38	$ 0.31	$ 0.96	$ 0.76
Diluted net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 0.37	$ 0.30	$ 0.95	$ 0.75
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING:
BASIC (in shares)	424,909	423,154	424,484	414,182
DILUTED (in shares)	429,004	426,933	428,529	418,303
DISTRIBUTIONS DECLARED PER COMMON SHARE (in dollars per share)	$ 0.53	$ 0.44	$ 1.04	$ 0.86
TV Azteca
OTHER INCOME (EXPENSE):
Interest income, TV Azteca, net of interest expense of $284, $370, $567 and $740, respectively	$ 2,748	$ 2,662	$ 5,464	$ 5,258
Interest expense	(284)	(370)	(567)	(740)
Excluding TV Azteca
OTHER INCOME (EXPENSE):
Interest income	6,468	4,404	10,002	7,368
Interest expense	$ (181,036)	$ (148,507)	$ (340,916)	$ (296,441)

CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Stock-based compensation expense	$ 21,907	$ 24,045	$ 49,986	$ 53,906
TV Azteca
Interest expense	284	370	567	740
Property
Stock-based compensation expense	392	390	899	822
Services
Stock-based compensation expense	255	98	406	237
Selling General Administrative And Development Expense
Stock-based compensation expense	21,260	23,557	48,681	52,847
Other Expense
Unrealized foreign currency (losses) gains	$ (24,585)	$ 25,461	$ 4,777	$ (30,007)

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 192,464	$ 157,180	$ 473,771	$ 352,672
Other comprehensive (loss) income:
Changes in fair value of cash flow hedges, net of tax benefit (expense) of $0, ($42), $0 and $9, respectively	(9)	597	65	(345)
Reclassification of unrealized (gains) losses on cash flow hedges to net income, net of tax benefit of $0, $22, $0 and $46, respectively	(57)	2,226	(65)	2,613
Foreign currency translation adjustments, net of tax expense (benefit) of $2,695, $197, $6,883 and ($12,412), respectively	(177,966)	(44,029)	48,326	(476,990)
Other comprehensive (loss) income	(178,032)	(41,206)	48,326	(474,722)
Comprehensive income (loss)	14,432	115,974	522,097	(122,050)
Comprehensive loss attributable to noncontrolling interests	12,712	17,421	6,610	37,123
Comprehensive income (loss) attributable to American Tower Corporation stockholders	$ 27,144	$ 133,395	$ 528,707	$ (84,927)

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net change in fair value of cash flow hedges, tax benefit (expense)	$ 0	$ (42)	$ 0	$ 9
Reclassification of unrealized losses on cash flow hedges to net income, tax benefit	0	22	0	46
Foreign currency translation adjustments, tax expense (benefit)	$ 2,695	$ 197	$ 6,883	$ (12,412)

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 473,771	$ 352,672
Adjustments to reconcile net income to cash provided by operating activities
Depreciation, amortization and accretion	739,399	591,876
Stock-based compensation expense	49,986	53,906
(Gain) loss on early retirement of long-term obligations	(830)	78,793
Other non-cash items reflected in statements of operations	53,464	75,531
Decrease in restricted cash	12,170	26,804
Increase in net deferred rent asset	(34,931)	(46,653)
Increase in assets	(32,984)	(99,179)
Increase in liabilities	51,271	2,710
Cash provided by operating activities	1,311,316	1,036,460
CASH FLOWS FROM INVESTING ACTIVITIES
Payments for purchase of property and equipment and construction activities	(319,427)	(311,122)
Payments for acquisitions, net of cash acquired	(1,216,467)	(670,246)
Payment for Verizon transaction	(4,748)	(5,060,416)
Proceeds from sale of short-term investments and other non-current assets	2,601	781,469
Payments for short-term investments	0	(816,038)
Deposits, restricted cash, investments and other	(5,360)	(3,087)
Cash used for investing activities	(1,543,401)	(6,079,440)
CASH FLOW FROM FINANCING ACTIVITIES
Repayments of short-term borrowings, net	(2,843)	0
Borrowings under credit facilities	1,326,866	4,740,308
Proceeds from issuance of senior notes, net	2,237,503	1,492,298
Proceeds from term loan	0	500,000
Proceeds from other borrowings	70,806	0
Proceeds from issuance of securities in securitization transaction, net	0	875,000
Repayments of notes payable, credit facilities and capital leases	(2,858,415)	(5,931,401)
Distributions to noncontrolling interest holders, net	(503)	(383)
Proceeds from stock options and ESPP	60,361	17,364
Distributions paid on common stock	(426,564)	(329,766)
Distributions paid on preferred stock	(53,563)	(31,085)
Proceeds from the issuance of common stock, net	0	2,440,327
Proceeds from the issuance of preferred stock, net	0	1,337,946
Payment for early retirement of long-term obligations	(125)	(86,107)
Deferred financing costs and other financing activities	(23,264)	(34,284)
Cash provided by financing activities	330,259	4,990,217
Net effect of changes in foreign currency exchange rates on cash and cash equivalents	(8,322)	13,973
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	89,852	(38,790)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	320,686	313,492
CASH AND CASH EQUIVALENTS, END OF PERIOD	410,538	274,702
Supplemental Cash Flow Elements [Abstract]
CASH PAID FOR INCOME TAXES (NET OF REFUNDS OF $14,011 AND $3,311, RESPECTIVELY)	50,413	29,911
CASH PAID FOR INTEREST	288,880	291,103
Decrease in accounts payable and accrued expenses for purchases of property and equipment and construction activities	(36,083)	(20,632)
Purchases of property and equipment under capital leases	21,651	10,510
Settlement of accounts receivable related to acquisitions	$ 0	$ 735

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Statement of Cash Flows [Abstract]
Income tax refunds	$ 14,011	$ 3,311

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	AOCI Attributable to Noncontrolling Interest [Member]	Series A Preferred Stock Convertible Preferred Stock Subject to Mandatory Redemption Preferred Stock	Series B Preferred Stock Convertible Preferred Stock Subject to Mandatory Redemption	Series B Preferred Stock Convertible Preferred Stock Subject to Mandatory Redemption Preferred Stock	Series B Preferred Stock Convertible Preferred Stock Subject to Mandatory Redemption Additional Paid-in Capital	Common Class A	Common Class A Common Stock	Common Class A Additional Paid-in Capital
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	49,161	$ 6		49,155
Stock based compensation related activity (shares)		672,300
Issuance of common stock	3,465			3,465
Issuance of common stock (shares)		43,940
Issuance of stock										$ 1,337,946	$ 14	$ 1,337,932	$ 2,440,327	$ 259	$ 2,440,068
Issuance of stock (shares)											1,375,000			25,850,000
Changes in fair value of cash flow hedges, net of tax	(345)				(340)		(5)
Reclassification of unrealized gains on cash flow hedges to net income	2,613				2,583		30
Foreign currency translation adjustment, net of tax	(476,990)				(436,543)		(40,447)
Contributions from noncontrolling interest holders	51						51
Distributions to noncontrolling interest holders	(434)						(434)
Common stock dividends/distributions declared	(365,450)					(365,450)
Preferred stock dividends declared	(23,210)					(23,210)
Net income	352,672					349,373	3,299
BALANCE at Jun. 30, 2015	7,373,158	$ 4,260	$ (207,740)	9,619,406	(1,228,521)	(876,607)	62,286		$ 60		$ 14
BALANCE (shares) at Jun. 30, 2015		426,074,991	(2,810,026)						6,000,000		1,375,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	352,672
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	86,780	$ 13		86,767
Stock based compensation related activity (shares)		1,331,272
Issuance of common stock	3,847			3,847
Issuance of common stock (shares)		44,733
Changes in fair value of cash flow hedges, net of tax	65				65
Reclassification of unrealized gains on cash flow hedges to net income	(65)				(65)
Foreign currency translation adjustment, net of tax	48,326				65,998		(665)	$ 65,333
Contributions from noncontrolling interest holders	13						13
Distributions to noncontrolling interest holders	(516)						(516)
Common stock dividends/distributions declared	(443,935)					(443,935)
Preferred stock dividends declared	(53,563)					(53,563)
Net income	473,771					462,709	6,739
BALANCE at Jun. 30, 2016	6,840,225	$ 4,280	$ (207,740)	$ 9,781,223	$ (1,770,998)	$ (1,033,324)	$ 66,710		$ 60		$ 14
BALANCE (shares) at Jun. 30, 2016		428,071,284	(2,810,026)						6,000,000		1,375,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	$ 469,448

DESCRIPTION OF BUSINESS, BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 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. On April 21, 2016, the Company significantly expanded its Asia segment portfolio by acquiring a 51% controlling ownership interest in 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 (the “Viom Acquisition”). Subsequent to the closing, Viom was renamed ATC Telecom Infrastructure Private Limited (“ATC TIPL”). 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 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 June 30, 2016, the Company’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 and six months ended June 30, 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. As of June 30, 2016, the Company has a controlling interest in two joint ventures in Ghana and Uganda with MTN Group Limited (“MTN Group”). The joint ventures are controlled by a holding company of which a wholly owned subsidiary of the Company holds a 51% interest and a wholly owned subsidiary of MTN Group holds a 49% interest. In addition, the Company holds an approximate 75% controlling interest in a subsidiary of the Company in South Africa and the South African investors hold an approximate 25% noncontrolling interest. The Company also holds a 51% controlling interest in ATC TIPL. 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 six months ended June 30, 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 its 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 standard is required to be applied using a modified retrospective approach for all leases existing at, or entered into after, the beginning of the earliest comparative period presented. 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 early adopted this standard in the second quarter of 2016 and elected to account for forfeitures as they occur, effective January 1, 2016. The adoption of this guidance was not material to the Company’s consolidated financial statements. Additionally, the Company elected to apply the prospective transition method to the amendments related to the presentation of excess tax benefits in the statements of cash flows.

GOODWILL AND OTHER INTANGIBLE ASSETS

6 Months Ended

Jun. 30, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL AND OTHER INTANGIBLE ASSETS

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



	Property										Services		Total
	U.S.		Asia (1)			EMEA			Latin America		Services		Total
Balance as of January 1, 2016	$	3,379,163	$	170,719		$	132,570		$	407,365	$	1,988	$	4,091,805
Additions	289		856,110			3,200			4,615		—		864,214
Effect of foreign currency translation	—		(16,714		)	(18,417		)	61,031		—		25,900
Balance as of June 30, 2016	$	3,379,452	$	1,010,115		$	117,353		$	473,011	$	1,988	$	4,981,919

_______________


(1)	Includes approximately $856.1 million of goodwill assumed in the Viom Acquisition (see note 13).

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



		As of June 30, 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	$	4,589,425	$	(1,175,676	)	$	3,413,749	$	3,980,281	$	(1,052,393	)	$	2,927,888
Acquired customer-related intangibles	15-20	10,139,104		(1,996,896		)	8,142,208		8,640,554		(1,763,853		)	6,876,701
Acquired licenses and other intangibles	3-20	28,756		(3,725		)	25,031		28,293		(5,486		)	22,807
Economic Rights, TV Azteca	70	20,267		(10,563		)	9,704		21,688		(11,208		)	10,480
Total other intangible assets		$	14,777,552	$	(3,186,860	)	$	11,590,692	$	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 June 30, 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 and six months ended June 30, 2016 was $185.3 million and $337.1 million, respectively, and amortization of intangible assets for the three and six months ended June 30, 2015 was $147.6 million and $258.1 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	$	356.6
2017	710.8
2018	708.6
2019	705.6
2020	686.8
2021	677.5

- 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

6 Months Ended

Jun. 30, 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
	June 30, 2016			December 31, 2015			Maturity Date
Series 2013-1A securities (1)	$	498,060		$	497,478		March 15, 2018
Series 2013-2A securities (2)	1,289,478			1,288,689			March 15, 2023
Series 2015-1 notes (3)	346,685			346,262			June 15, 2020
Series 2015-2 notes (4)	519,106			518,776			June 16, 2025
2012 GTP notes (5)	182,233			281,902			March 15, 2019
Unison notes (6)	201,054			201,930			Various
Viom indebtedness (7)	698,274			—			Various
Viom preference shares (8)	24,682			—			Various
Shareholder loans (9)	154,387			145,540			Various
BR Towers debentures (10)	105,191			85,219			October 15, 2023
Colombian credit facility (11)	61,060			59,640			April 24, 2021
South African facility (12)	50,230			53,175			December 17, 2020
Brazil credit facility (13)	31,293			21,868			January 15, 2022
Indian working capital facility (14)	5,688			8,752			July 31, 2016
Total American Tower subsidiary debt	4,167,421			3,509,231

2013 Credit Facility	72,203			1,225,000			June 28, 2019
Term Loan	1,994,238			1,993,601			January 29, 2021
2014 Credit Facility	1,840,000			1,980,000			January 29, 2021
4.500% senior notes	997,944			997,693			January 15, 2018
3.40% senior notes	999,532			999,769			February 15, 2019
7.25% senior notes	296,389			296,242			May 15, 2019
2.800% senior notes	744,239			743,557			June 1, 2020
5.050% senior notes	696,916			697,216			September 1, 2020
3.300% senior notes	744,121			—			February 15, 2021
3.450% senior notes	643,216			642,786			September 15, 2021
5.900% senior notes	497,037			497,188			November 1, 2021
4.70% senior notes	695,671			695,374			March 15, 2022
3.50% senior notes	988,231			987,966			January 31, 2023
5.00% senior notes	1,002,735			1,003,453			February 15, 2024
4.000% senior notes	739,539			739,057			June 1, 2025
4.400% senior notes	494,957			—			February 15, 2026
3.375% senior notes	982,645			—			October 15, 2026
Total American Tower Corporation debt	14,429,613			13,498,902
Other debt, including capital lease obligations	120,042			110,876
Total	18,717,076			17,119,009
Less current portion of long-term obligations	(314,063		)	(50,202		)
Long-term obligations	$	18,403,013		$	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 its acquisition of MIP Tower Holdings LLC. Maturity date represents anticipated repayment date; final legal maturity is March 15, 2042. During the six months ended June 30, 2016, the Company repaid the $94.1 million outstanding under the Secured Tower Cellular Site Revenue Notes, Series 2012-1 Class A and released 472 sites in connection with the repayment.


(6)	Secured debt assumed by the Company in connection with its 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)	Debt primarily assumed by the Company in connection with the Viom Acquisition. Maturity dates begin March 31, 2017. In June 2016, the Company refinanced 4.75 billion Indian Rupees (“INR”) of Viom assumed indebtedness with a new short-term committed loan facility with a borrowing capacity of 5.80 billion INR ($85.9 million as of June 30, 2016). Denominated in INR.


(8)	Mandatorily redeemable preference shares issued by Viom. The shares are to be redeemed in equal parts on March 26, 2017 and March 26, 2018.


(9)	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.


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


(11)	Denominated in Colombian Pesos and amortizes through April 24, 2021.


(12)	Denominated in South African Rand and amortizes through December 17, 2020.


(13)	Denominated in BRL.


(14)	Denominated in INR. This agreement provides that the maturity date may be extended for additional 30-day periods.

Current portion of long-term obligations—The Company’s current portion of long-term obligations includes (i)13.1 billion INR ($194.7 million) of indebtedness primarily assumed by the Company in connection with the Viom Acquisition, including 4.75 billion INR ($70.3 million) outstanding under a short-term committed loan facility which was used to refinance a Viom term loan, (ii) 0.8 billion INR ($12.3 million) related to Viom preference shares, and (iii) $67.4 million outstanding under the Secured Cellular Site Revenue Notes, Series 2010-1 Class C (included in the Unison notes) assumed in connection with the acquisition of Unison.

Viom indebtedness—Amounts outstanding and key terms of the Viom indebtedness consisted of the following as of June 30, 2016 (in millions):



	Amount Outstanding (INR)	Amount Outstanding (USD)		Interest Rate (Range)		Maturity Date (Range)
Term loans	39,745	$	588.6	8.75% - 11.20%		March 31, 2017 - November 30, 2024
Debenture	6,000	$	88.9	9.90	%	April 28, 2020
Working capital facilities	1,406	$	20.8	11.05% - 11.60%		October 23, 2016 - March 18, 2017

The Viom indebtedness includes several term loans, ranging from one to ten years, which are generally secured by the borrower’s short-term and long-term assets. The term loans bear interest at the bank’s Marginal Cost of Funds based Lending Rate or the bank’s base rate, plus spreads ranging from 1.00% to 1.55%. Interest rates on the term loans are fixed until certain annual reset dates. Generally, the term loans can be repaid without penalty on the annual reset dates; earlier repayments require notice to the lenders and are subject to prepayment penalties, typically of 1% to 2%. Scheduled repayment terms include either ratable or staggered amortization with repayments typically commencing between six and 36 months after the initial disbursement of funds.

The debenture is secured by the borrower’s long-term assets, including property and equipment and intangible assets. The debenture bears interest at a base rate plus a spread of 0.6%. The base rate is set in advance for each quarterly coupon period. Should the actual base rate be less than 10.25% or greater than 9.75%, the revised base rate is assumed to be 10.00% for purposes of the reset. Additionally, the spread is subject to reset 36 and 48 months from the issuance date of April 27, 2015. The holders of the debenture must reach a consensus on the revised spread and the borrower must redeem all of the debentures held by holders from whom consensus is not achieved. Additionally, the debenture is required to be redeemed by the borrower if it does not maintain a minimum credit rating.

The Viom indebtedness includes several working capital facilities, most of which are subject to annual renewal, which are generally secured by the borrower’s short-term and long-term assets. The working capital facilities bear interest at rates that are comprised of base rates plus spreads ranging from 1.60% to 2.30%. Generally, the working capital facilities are payable on demand prior to maturity.

Viom preference shares—As of June 30, 2016, ATC TIPL had 166,666,666 mandatorily redeemable preference shares (the “Preference Shares”) outstanding, which are required to be redeemed in cash. Accordingly, the Company recognized debt of 1.67 billion INR ($24.7 million) related to the Preference Shares outstanding on the consolidated balance sheet.

Unless redeemed earlier, the Preference Shares will be redeemed in two equal installments on March 26, 2017 and March 26, 2018 in an amount equal to ten INR per share along with a redemption premium, as defined in the investment agreement, which equates to a compounded return of 13.5% per annum. ATC TIPL, at its option, may redeem the Preference Shares prior to the aforementioned dates, subject to an additional 2% redemption premium.

Senior Notes Offerings

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.

3.375% Senior Notes Offering—On May 13, 2016, the Company completed a registered public offering of $1.0 billion aggregate principal amount of 3.375% senior unsecured notes due 2026 (the “3.375% Notes”). The net proceeds from this offering were approximately $981.5 million, after deducting commissions and estimated expenses. The Company used the proceeds to repay existing indebtedness under the 2013 Credit Facility.

The 3.375% Notes will mature on October 15, 2026 and bear interest at a rate of 3.375% per annum. Accrued and unpaid interest on the notes will be payable in U.S. Dollars semi-annually in arrears on April 15 and October 15 of each year, beginning on October 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 May 13, 2016.

The Company may redeem each series of 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, the 4.400% Notes on or after November 15, 2025 or the 3.375% Notes on or after July 15, 2026, it will not be required to pay a make-whole premium. In addition, if the Company undergoes a change of control and corresponding ratings decline, each as defined in the applicable supplemental indenture, it may be required to repurchase all of the applicable notes at a purchase price equal to 101% of the principal amount of such notes, plus accrued and unpaid interest (including additional interest, if any), up to but not including the repurchase date. The notes rank equally with all of the Company’s other senior unsecured debt and are structurally subordinated to all existing and future indebtedness and other obligations of its subsidiaries.

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

Bank Facilities

2013 Credit Facility—During the six months ended June 30, 2016, the Company borrowed an aggregate of $1.2 billion and repaid an aggregate of $2.4 billion of revolving indebtedness under the 2013 Credit Facility. The Company primarily used the borrowings to fund the Viom Acquisition. On July 15, 2016, the Company borrowed $110.0 million under the 2013 Credit Facility.

2014 Credit Facility—During the six months ended June 30, 2016, the Company borrowed an aggregate of $80.0 million and repaid an aggregate of $220.0 million of revolving indebtedness under its senior unsecured revolving credit facility entered into in January 2012 and amended and restated in September 2014, as further amended (the “2014 Credit Facility”).

As of June 30, 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”) were as follows:



	Outstanding Principal Balance (in millions)		Undrawn letters of credit (in millions)		Maturity Date	Current margin over LIBOR (1)		Current commitment fee (2)
2013 Credit Facility	$	72.2	$	3.2	June 28, 2019 (3)	1.250	%	0.150	%
2014 Credit Facility	$	1,840.0	$	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 each credit facility.

(3) Subject to two optional renewal periods.

FAIR VALUE MEASUREMENTS

6 Months Ended

Jun. 30, 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):



	June 30, 2016				December 31, 2015
	Fair Value Measurements Using				Fair Value Measurements Using
	Level 2		Level 3		Level 2		Level 3
Assets:
Interest rate swap agreements	$	751	—		$	692	—
Embedded derivative in lease agreement	—		$	13,735	—		$	14,176
Liabilities:
Acquisition-related contingent consideration	—		$	12,225	—		$	12,436

During the six months ended June 30, 2016, the Company has made no changes to the methods described in note 11 to the Company’s consolidated financial statements in the 2015 Form 10-K that it used to measure the fair value of its interest rate swap agreements, the embedded derivative in one of its lease agreements and acquisition-related contingent consideration. The changes in fair value during the six months ended June 30, 2016 and 2015 were not material to the consolidated financial statements. As of June 30, 2016, the Company estimated the value of all potential acquisition-related contingent consideration required payments to be between zero and $26.3 million.

Redeemable Noncontrolling Interests

In connection with the Viom Acquisition, the Company entered into a shareholders’ agreement that provides for put options held by certain noncontrolling shareholders (see note 9). The fair value of the Company’s noncontrolling interests reflected on the consolidated balance sheet are determined using a discounted cash flow approach, which takes into consideration Level 3 unobservable inputs and applies a discount factor.

The fair value of the redeemable noncontrolling interests was $1.1 billion at the date of acquisition and was recorded in

Redeemable noncontrolling interests in the consolidated balance sheet.

See notes 9 and 13 for more information.

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 and six months ended June 30, 2016 and 2015, the Company did not record any material asset impairment charges.

There were no other items measured at fair value on a nonrecurring basis during the six months ended June 30, 2016.

Fair Value of Financial Instruments—The Company’s financial instruments for which the carrying value reasonably approximates fair value at June 30, 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 June 30, 2016 and December 31, 2015, the carrying value of long-term obligations, including the current portion, was $18.7 billion and $17.1 billion, respectively. As of June 30, 2016, the fair value of long-term obligations, including the current portion, was $19.5 billion, of which $11.3 billion was measured using Level 1 inputs and $8.2 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	6 Months Ended
INCOME TAXES	Jun. 30, 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 (“ETR”) for the full fiscal year. Cumulative adjustments to the Company’s estimate are recorded in the interim period in which a change in the estimated annual ETR is determined. 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 described in note 1, effective January 1, 2016, the Company adopted new guidance on the accounting for share-based payment transactions. As part of this new guidance, excess windfall tax benefits and tax deficiencies related to the Company’s stock option exercises and restricted stock unit vestings are recognized as an income tax benefit or expense in the consolidated statements of operations in the period in which the deduction occurs. Excess windfall tax benefits and tax deficiencies are, therefore, not anticipated when determining the annual ETR and are instead recognized in the interim period in which those items occur. As of June 30, 2016 and December 31, 2015, the total unrecognized tax benefits that would impact the ETR, if recognized, were approximately $68.6 million and $28.1 million, respectively. The amount of unrecognized tax benefits during the three and six months ended June 30, 2016 includes additions to the Company’s existing tax positions of $32.8 million and $39.3 million, respectively, both of which include $23.8 million of tax positions assumed through acquisition, and foreign currency fluctuations of $0.4 million and $1.2 million, respectively. 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 $14.1 million. The Company recorded penalties and income tax-related interest expense during the three and six months ended June 30, 2016 of $2.2 million and $5.2 million, respectively, and during the three and six months ended June 30, 2015 of $0.6 million and $1.5 million, respectively. As of June 30, 2016 and December 31, 2015, the total amount of accrued income tax related interest and penalties included in the consolidated balance sheets was $25.0 million and $20.2 million, respectively.

STOCK-BASED COMPENSATION

6 Months Ended

Jun. 30, 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 June 30, 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. In addition, the Company maintains an employee stock purchase plan (“ESPP”) pursuant to which eligible employees may purchase shares of the Company’s common stock on the last day of each bi-annual offering period at a 15% discount of the lower of the closing market value on the first or last day of such offering period. The offering periods run from June 1 through November 30 and from December 1 through May 31 of each year.

The Company recognized stock-based compensation expense of $21.9 million and $50.0 million during the three and six months ended June 30, 2016, respectively, and recognized stock-based compensation expense of $24.0 million and $53.9 million during the three and six months ended June 30, 2015, respectively. The Company capitalized $0.1 million and $0.8 million of stock-based compensation expense as property and equipment during the three and six months ended June 30, 2016, respectively, and capitalized $0.6 million and $1.1 million of stock-based compensation expense as property and equipment during the three and six months ended June 30, 2015, respectively.

Stock Options—The fair value of each option granted during the six months ended June 30, 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 during the six months ended June 30, 2016 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 six months ended June 30, 2016 was $14.56. As of June 30, 2016, total unrecognized compensation expense related to unvested stock options was $34.8 million, which is expected to be recognized over a weighted average period of approximately two years.

The Company’s option activity for the six months ended June 30, 2016 was as follows:



	Number of Options
Outstanding as of January 1, 2016	7,680,819
Granted	1,132,596
Exercised	(907,829	)
Forfeited	(16,320	)
Expired	(500	)
Outstanding as of June 30, 2016	7,888,766

Restricted Stock Units—As of June 30, 2016, total unrecognized compensation expense related to unvested RSUs granted under the 2007 Plan was $115.6 million and is expected to be recognized over a weighted average period of approximately three years.

Performance-Based Restricted Stock Units—During the six months ended June 30, 2016, the Compensation Committee granted an aggregate of 169,340 PSUs to its executive officers (the “2016 PSUs”) and established the performance metrics for this award. During the six months ended June 30, 2015, the Compensation Committee granted an aggregate of 70,135 PSUs to its executive officers (the “2015 PSUs”) and established the performance metric for this award. 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 June 30, 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 was not included in the table below.

Restricted Stock Units and Performance-Based Restricted Stock Units—The Company’s RSU and PSU activity for the six months ended June 30, 2016 was as follows:



	RSUs		PSUs
Outstanding as of January 1, 2016 (1)	1,656,993		33,377
Granted (2)	767,421		192,719
Vested	(635,126	)	—
Forfeited	(54,053	)	—
Outstanding as of June 30, 2016	1,735,235		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 and six months ended June 30, 2016, the Company recorded $2.4 million and $3.2 million, respectively, in stock-based compensation expense for equity awards in which the performance goals had been established and were probable of being achieved. The remaining unrecognized compensation expense related to these awards at June 30, 2016 was $16.6 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

REDEEMABLE NONCONTROLLING INTERESTS

6 Months Ended

Jun. 30, 2016

Noncontrolling Interest [Abstract]

REDEEMABLE NONCONTROLLING INTERESTS

Redeemable Noncontrolling Interests—In connection with the Viom Acquisition, the Company, through one of its subsidiaries, entered into a shareholders agreement (the “Shareholders Agreement”) with Viom and the following remaining Viom shareholders: Tata Sons Limited, Tata Teleservices Limited, IDFC Private Equity Fund III, Macquarie SBI Investments Pte Limited and SBI Macquarie Infrastructure Trust (collectively, the “Remaining Shareholders”). The Shareholders Agreement provides for, among other things, put options held by certain of the Remaining Shareholders, which allow the Remaining Shareholders to sell outstanding shares of ATC TIPL, and call options held by the Company, which allow the Company to buy the nonontrolling shares of ATC TIPL. The put options, which are not under the Company’s control, cannot be separated from the noncontrolling interests. As a result, the combination of the noncontrolling interests and the redemption feature require classification as redeemable noncontrolling interests in the consolidated balance sheet, separate from equity.

Given the provisions governing the put rights, the redeemable noncontrolling interests are recorded outside of permanent equity at their redemption value. The noncontrolling interests become redeemable after the passage of time, and therefore the Company records the carrying amount of the noncontrolling interests at the greater of (i) the initial carrying amount, increased or decreased for the noncontrolling interests’ share of net income or loss, and (ii) the redemption value. If required, the Company will adjust the redeemable noncontrolling interests to redemption value on each balance sheet date with changes in redemption value recognized as an adjustment to Distributions in excess of earnings.

The put options may be exercised, requiring the Company to purchase the Remaining Shareholders’ equity interests, on specified dates beginning April 1, 2018 through March 31, 2021. The price of the put options will be based on the fair market value of the exercising Remaining Shareholder’s interest in the Company’s India operations at the time the option is exercised. Put options held by certain of the Remaining Shareholders are subject to a floor price of 216 INR per share.

The following is a reconciliation of the changes in the Redeemable noncontrolling interests (in thousands):



Balance as of January 1, 2016	$	—
Fair value at acquisition	1,097,841
Net income attributable to noncontrolling interests	4,323
Foreign currency translation adjustment attributable to noncontrolling interests	(17,007		)
Balance as of June 30, 2016	$	1,085,157