American Tower (AMT) 10-Q 3 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 26, 2019
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, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		442,023,435

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 1,004.8	$ 1,208.7
Restricted cash	94.9	96.2
Short-term investments	18.4	0
Accounts receivable, net	473	459
Prepaid and other current assets	471.2	621.2
Total current assets	2,062.3	2,385.1
PROPERTY AND EQUIPMENT, net	11,202.6	11,247.1
GOODWILL	5,538.2	5,501.9
OTHER INTANGIBLE ASSETS, net	11,042.8	11,174.3
DEFERRED TAX ASSET	132.3	157.7
DEFERRED RENT ASSET	1,588.6	1,581.7
RIGHT-OF-USE ASSET	7,080.9	0
NOTES RECEIVABLE AND OTHER NON-CURRENT ASSETS	279.1	962.6
TOTAL	38,926.8	33,010.4
CURRENT LIABILITIES:
Accounts payable	130	130.8
Accrued expenses	863.7	948.3
Distributions payable	403.1	377.4
Accrued interest	126.5	174.5
Current portion of operating lease liability	498.4	0
Current portion of long-term obligations	2,097.2	2,754.8
Unearned revenue	293	304.1
Total current liabilities	4,411.9	4,689.9
LONG-TERM OBLIGATIONS	19,107.1	18,405.1
OPERATING LEASE LIABILITY	6,316.1	0
ASSET RETIREMENT OBLIGATIONS	1,227.2	1,210
DEFERRED TAX LIABILITY	510.8	535.9
OTHER NON-CURRENT LIABILITIES	864.4	1,265.1
Total liabilities	32,437.5	26,106
COMMITMENTS AND CONTINGENCIES
REDEEMABLE NONCONTROLLING INTERESTS	589	1,004.8
EQUITY (shares in thousands):
Common stock: $.01 par value; 1,000,000 shares authorized; 452,525 and 451,617 shares issued; and 441,968 and 441,060 shares outstanding, respectively	4.5	4.5
Additional paid-in capital	10,447.9	10,380.8
Distributions in excess of earnings	(1,226.4)	(1,199.5)
Accumulated other comprehensive loss	(2,672.2)	(2,642.9)
Treasury stock (10,557 shares at cost)	(1,206.8)	(1,206.8)
Total American Tower Corporation equity	5,347	5,336.1
Noncontrolling interests	553.3	563.5
Total equity	5,900.3	5,899.6
TOTAL	$ 38,926.8	$ 33,010.4

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	452,525,000	451,617,000
Common stock, shares outstanding	441,968,000	441,060,000
Treasury stock, shares	10,557,000	10,557,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
REVENUES:
Property	$ 1,786,000	$ 1,710,400
Services	27,400	31,400
Total operating revenues	1,813,400	1,741,800
Costs of operations (exclusive of items shown separately below):
Property	533,000	507,400
Services	10,400	12,500
Depreciation, amortization and accretion	436,900	446,300
Selling, general, administrative and development expense	198,100	204,900
Other operating expenses	20,100	167,800
Total operating expenses	1,198,500	1,338,900
OPERATING INCOME	614,900	402,900
OTHER INCOME (EXPENSE):
Loss on retirement of long-term obligations	(100)	0
Other income (including foreign currency gains of $20.1 and $23.3, respectively)	21,900	27,800
Total other expense	(173,300)	(153,700)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	441,600	249,200
Income tax (provision) benefit	(34,000)	31,100
NET INCOME	407,600	280,300
Net (income) loss attributable to noncontrolling interests	(10,200)	4,900
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION STOCKHOLDERS	397,430	285,200
Dividends on preferred stock	0	(9,400)
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION COMMON STOCKHOLDERS	$ 397,430	$ 275,800
NET INCOME PER COMMON SHARE AMOUNTS:
Basic net income attributable to American Tower Corporation common stockholders (in dollars per share)	$ 0.90	$ 0.63
Diluted net income attributable to American Tower Corporation common stockholders (in dollars per share)	$ 0.89	$ 0.63
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING (in thousands):
BASIC (in shares)	441,351	435,124
DILUTED (in shares)	444,621	438,520
TV Azteca
OTHER INCOME (EXPENSE):
Interest income, TV Azteca (net of interest expense of $0.0 and $0.3, respectively)	$ 0	$ 2,700
Interest expense	0	(300)
Excluding TV Azteca
OTHER INCOME (EXPENSE):
Interest income	12,400	15,400
Interest expense	$ (207,500)	$ (199,600)

CONSOLIDATED STATEMENTS OF OP_2

CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Unrealized foreign currency gains (losses)	$ 20.1	$ 23.3
TV Azteca
Interest expense	$ 0	$ 0.3

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 407.6	$ 280.3
Other comprehensive income (loss):
Changes in fair value of cash flow hedges, each net of tax expense of $0	(0.1)	0
Reclassification of unrealized losses on cash flow hedges to net income, each net of tax expense of $0	0.1	0.1
Adjustment to redeemable noncontrolling interest	0	78.8
Foreign currency translation adjustments, net of tax expense of $1.0 and $1.6, respectively	12.9	57.6
Other comprehensive income	12.9	136.5
Comprehensive income	420.5	416.8
Allocation of accumulated other comprehensive income resulting from purchase of redeemable noncontrolling interest	(52.4)	0
Comprehensive loss attributable to noncontrolling interest	0	12.1
Comprehensive income attributable to American Tower Corporation stockholders	$ 368.1	$ 428.9

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Changes in fair value of cash flow hedges, tax	$ 0	$ 0
Reclassification of unrealized gains on cash flow hedges to net income, tax	0	0
Foreign currency translation adjustments, tax expense (benefit)	$ 1	$ 1.6

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 407.6	$ 280.3
Adjustments to reconcile net income to cash provided by operating activities
Depreciation, amortization and accretion	436.9	446.3
Amortization of operating leases	152.6	0
Stock-based compensation expense	42.5	42.7
Loss on early retirement of long-term obligations	0.1	0
Other non-cash items reflected in statements of operations	28.9	96.8
Increase in net deferred rent balances	(5.3)	(3.9)
Reduction in operating lease liability	(132.4)	0
Increase in assets	(33)	(95.4)
(Decrease) increase in liabilities	(112.8)	25
Cash provided by operating activities	785.1	791.8
CASH FLOWS FROM INVESTING ACTIVITIES
Payments for purchase of property and equipment and construction activities	(220.8)	(198.5)
Payments for acquisitions, net of cash acquired	(91.1)	(673.4)
Proceeds from sale of short-term investments and other non-current assets	254.9	84
Payments for short-term investments	(261.5)	(478.1)
Deposits and other	(4.8)	(14.6)
Cash used for investing activities	(323.3)	(1,280.6)
CASH FLOWS FROM FINANCING ACTIVITIES
Borrowings under credit facilities	1,700	1,748.3
Proceeds from issuance of senior notes, net	1,241.6	0
Proceeds from term loan	1,300	1,500
Proceeds from issuance of securities in securitization transaction	0	500
Repayments of notes payable, credit facilities, senior notes, secured debt, term loan, finance leases and capital leases	(4,025.9)	(2,584.9)
Distributions to noncontrolling interest holders, net	(13.8)	(0.3)
Proceeds from stock options	27.2	20
Distributions paid on common stock	(377.1)	(304.3)
Distributions paid on preferred stock	0	(18.9)
Deferred financing costs and other financing activities	(76.7)	(42.6)
Purchase of redeemable noncontrolling interest	(425.7)	0
Cash (used for) provided by financing activities	(650.4)	817.3
Net effect of changes in foreign currency exchange rates on cash and cash equivalents, and restricted cash	(16.6)	(4.5)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS, AND RESTRICTED CASH	(205.2)	324
CASH AND CASH EQUIVALENTS, AND RESTRICTED CASH, BEGINNING OF PERIOD	1,304.9	954.9
CASH AND CASH EQUIVALENTS, AND RESTRICTED CASH, END OF PERIOD	1,099.7	1,278.9
CASH PAID FOR INCOME TAXES (NET OF REFUNDS OF $0.3 AND $4.7, RESPECTIVELY)	36.9	24.7
CASH PAID FOR INTEREST	249	228.6
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Decrease in accounts payable and accrued expenses for purchases of property and equipment and construction activities	(17.7)	(29.3)
Purchases of property and equipment under finance leases, perpetual easements and capital leases	$ 16	$ 9.7

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Cash Flows [Abstract]
Income tax refunds	$ 0.3	$ 4.7

CONSOLIDATED STATEMENTS OF EQUI

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Thousands, $ in Millions	Total	Preferred StockPreferred Stock - Series BConvertible Preferred Stock Subject to Mandatory Redemption	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Distributions in Excess of Earnings	Noncontrolling Interest
BALANCE at Dec. 31, 2017	$ 6,828.1	$ 0	$ 4.4	$ (974)	$ 10,247.5	$ (1,978.3)	$ (1,058.1)	$ 586.6
BALANCE (shares) at Dec. 31, 2017		1,375	437,729	(8,909)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation related activity	27.3		$ 0		27.3
Stock-based compensation related activity (shares)			756
Conversion of preferred stock		$ 0	$ 0.1		(0.1)
Conversion of preferred stock (shares)		(1,375)	12,020
Changes in fair value of cash flow hedges, net of tax	0					0
Reclassification of unrealized losses on cash flow hedges to net income, net of tax	(0.1)					(0.1)
Foreign currency translation adjustment, net of tax	79.9					64.8		15.1
Adjustment to redeemable noncontrolling interest	28.1				(50.7)	78.8
Distributions to noncontrolling interest	(0.3)							(0.3)
Purchase of redeemable noncontrolling interest	0
Common stock distributions declared							(332.3)
Preferred stock dividends declared	(18.9)						(18.9)
Net income	290.9						285.2	5.7
BALANCE at Mar. 31, 2018	6,941.3	$ 0	$ 4.5	$ (974)	10,224	(1,834.6)	(1,085.7)	607.1
BALANCE (shares) at Mar. 31, 2018		0	450,505	(8,909)
BALANCE at Dec. 31, 2018	5,899.6	$ 0	$ 4.5	$ (1,206.8)	10,380.8	(2,642.9)	(1,199.5)	563.5
BALANCE (shares) at Dec. 31, 2018		0	451,617	(10,557)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation related activity	14.7		$ 0		14.7
Stock-based compensation related activity (shares)			908
Changes in fair value of cash flow hedges, net of tax	(0.1)					(0.1)
Reclassification of unrealized losses on cash flow hedges to net income, net of tax	(0.1)					(0.1)
Foreign currency translation adjustment, net of tax	3					23.1		(20.1)
Distributions to noncontrolling interest	(0.3)							(0.3)
Purchase of redeemable noncontrolling interest	(425.7)				52.4	(52.4)
Common stock distributions declared	(399.6)						(399.6)
Net income	407.6						397.4	10.2
BALANCE at Mar. 31, 2019	$ 5,900.3	$ 0	$ 4.5	$ (1,206.8)	$ 10,447.9	$ (2,672.2)	$ (1,226.4)	$ 553.3
BALANCE (shares) at Mar. 31, 2019		0	452,525	(10,557)

BASIS OF PRESENTATION AND SIGNI

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES The accompanying consolidated and condensed consolidated financial statements have been prepared by American Tower Corporation (together with its subsidiaries, “ATC” or the “Company”) pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The financial information included herein is unaudited. However, the Company believes that all adjustments, which are of a normal and recurring nature, considered necessary for a fair presentation of its financial position and results of operations for such periods have been included herein. The consolidated and condensed consolidated financial statements and related notes should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 (the “ 2018 Form 10-K”). The results of operations for the three months ended March 31, 2019 are not necessarily indicative of the results that may be expected for the entire year. Principles of Consolidation and Basis of Presentation —The accompanying consolidated and condensed consolidated financial statements include the accounts of the Company and those entities in which it has a controlling interest. Investments in entities that the Company does not control are accounted for using the equity 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 March 31, 2019 , the Company holds (i) a 51% controlling interest in each of two joint ventures, one in Ghana and one in Uganda, (MTN Group Limited holds a 49% noncontrolling interest), (ii) a 51% controlling interest in a joint venture that primarily consists of the Company’s operations in Germany and France (PGGM holds a 49% noncontrolling interest), (iii) an approximate 81% controlling interest in a subsidiary of the Company in South Africa (South African investors hold an approximate 19% noncontrolling interest) and (iv) a 79% controlling interest in ATC Telecom Infrastructure Private Limited (“ATC TIPL”), formerly Viom Networks Limited (“Viom”), in India. Significant Accounting Policies —The Company’s significant accounting policies are described in note 1 to the Company’s consolidated financial statements included in the 2018 Form 10-K. There have been no material changes to the Company’s significant accounting policies during the three months ended March 31, 2019 , except the adoption of new lease accounting guidance, as discussed below. Cash and Cash Equivalents and Restricted Cash —The reconciliation of cash and cash equivalents and restricted cash reported within the applicable balance sheet that sum to the total of the same such amounts shown in the statement of cash flows is as follows: Three Months Ended March 31, 2019 2018 Cash and cash equivalents $ 1,004.8 $ 1,125.4 Restricted cash 94.9 153.5 Total cash and cash equivalents and restricted cash $ 1,099.7 $ 1,278.9 Lease —The new lease standard requires leases to be accounted for using a right-of-use model, which recognizes that, at the date of commencement, a lessee has a financial obligation to make lease payments to the lessor for the right to use the underlying asset during the lease term. The lessee recognizes a corresponding right-of-use asset related to this right. On January 1, 2019, the Company elected to adopt the new lease standard using the modified retrospective method applied to lease arrangements that were in place on the transition date. Results for reporting periods beginning January 1, 2019 are presented under the new standard, while prior-period amounts are not adjusted and continue to be reported in accordance with accounting under the previously applicable guidance. The Company elected certain available practical expedients which permit the adopter to not reassess certain items upon adoption, including: (i) whether any existing contracts are or contain leases, (ii) the classification of existing leases and (iii) initial direct costs for existing leases. The Company also elected the practical expedient related to easements, which permits carryforward accounting treatment for land easements on existing agreements. The Company recorded a net increase to opening Distributions in excess of earnings in its consolidated balance sheet of $24.7 million as of January 1, 2019 due to the cumulative impact of adopting the new lease standard. This adjustment related to right-of-use asset impairments. The Company also recorded a lease liability of $6.9 billion and a corresponding right-of-use asset of $7.1 billion upon adoption of the new lease standard. Those rights and obligations are primarily related to operating leases for ground space underneath the Company’s communications sites. The right-of-use assets recorded include, among other items, amounts previously classified as prepaid rent, deferred lease acquisition costs, fair value adjustments on acquired leases and long-term deferred rent obligations. Finance leases, which primarily relate to towers, equipment and vehicles, were largely unchanged. There was no significant change to the Company’s consolidated statement of operations resulting from the adoption of this standard. The Company did not elect the practical expedient for short-term leases, which permits an adopter to not apply the lease standard to leases with a remaining maturity of one year or less, and applied the new lease accounting standard to all leases, including short-term leases. In conjunction with the adoption of the new lease accounting guidance, the Company applied the lessor and lessee practical expedient and no longer separates lease and non-lease components within a lease agreement when the timing and pattern of revenue recognition for the components are the same and the combined single lease component is classified as an operating lease. Certain amounts, such as power and fuel and common area maintenance, which were previously reported as non-lease revenue, are now accounted for as lease revenue. Accordingly, the Company has reclassified certain prior-period amounts within its disclosures. Revenue —Most of the Company’s revenue is derived from leasing arrangements and is accounted for as lease revenue unless the timing and pattern of revenue recognition differs from the lease components. Revenue related to distributed antenna system (“DAS”) networks and fiber results from agreements with tenants that are not leases. Non-lease revenue —Non-lease revenue consists primarily of revenue generated from DAS networks, fiber and other property related revenue. DAS networks and fiber arrangements require that the Company provide the tenant the right to use the applicable communications infrastructure. Performance obligations are satisfied over time for the duration of the arrangements. Other property related revenue streams, which include site inspections, are not material on either an individual or consolidated basis. Services revenue —The Company offers tower-related services in the United States. These services include site acquisition, zoning and permitting (“AZP”) and structural analysis. There is a single performance obligation related to AZP, and revenue is recognized over time based on milestones achieved, which are determined based on costs expected to be incurred. Structural analysis services may have more than one performance obligation, contingent upon the number of contracted services. Revenue is recognized at the point in time the services are completed. A summary of non-lease revenue disaggregated by source and geography is as follows: Three Months Ended March 31, 2019 U.S. Asia EMEA Latin America Total Non-lease property revenue $ 58.8 $ 2.4 $ 1.6 $ 35.0 $ 97.8 Services revenue 27.4 — — — 27.4 Total non-lease revenue $ 86.2 $ 2.4 $ 1.6 $ 35.0 $ 125.2 Property lease revenue 927.5 286.5 175.9 298.3 1,688.2 Total revenue $ 1,013.7 $ 288.9 $ 177.5 $ 333.3 $ 1,813.4 Three Months Ended March 31, 2018 (1) U.S. Asia EMEA Latin America Total Non-lease property revenue $ 63.1 $ 1.9 $ 0.6 $ 23.7 $ 89.3 Services revenue 31.4 — — — 31.4 Total non-lease revenue $ 94.5 $ 1.9 $ 0.6 $ 23.7 $ 120.7 Property lease revenue 868.3 271.1 173.6 308.1 1,621.1 Total revenue $ 962.8 $ 273.0 $ 174.2 $ 331.8 $ 1,741.8 _______________ (1) Prior-period amounts adjusted with the adoption of the new lease accounting guidance, as applicable. Information about receivables, contract assets and contract liabilities from contracts with tenants is as follows: March 31, 2019 December 31, 2018 (1) Accounts receivable $ 91.9 $ 92.6 Prepaids and other current assets 7.7 7.7 Notes receivable and other non-current assets 21.3 22.2 Unearned revenue (2) 43.2 35.0 Other non-current liabilities (3) 54.1 54.1 _______________ (1) Prior-period amounts adjusted with the adoption of the new lease accounting guidance, as applicable. (2) Excludes $55.9 million and $55.0 million of capital contributions related to DAS networks as of March 31, 2019 and December 31, 2018, respectively. (3) Excludes $302.6 million and $313.6 million of capital contributions related to DAS networks as of March 31, 2019 and December 31, 2018, respectively. The Company records unearned revenue when payments are received from tenants in advance of the completion of the Company’s performance obligations. Long-term unearned revenue is included in Other non-current liabilities. The increase in the Unearned revenue for the three months ended March 31, 2019 is due to payments received, offset by $14.1 million of revenue recognized this period that was included in the Unearned revenue balance as of December 31, 2018. During the three months ended March 31, 2018, the Company recognized $10.4 million of revenue from the Unearned revenue balance as of January 1, 2018. The Company also recognized revenues of $14.5 million and $13.8 million for capital contributions related to DAS networks during the three months ended March 31, 2019 and 2018, respectively. There was $0.1 million of revenue recognized from Other non-current liabilities during each of the three months ended March 31, 2019 and 2018. The Company records unbilled receivables, which are included in Prepaids and other current assets, when it has completed a performance obligation prior to its ability to bill under the customer arrangement. Other contract assets are included in Notes receivable and other non-current assets. The decrease in unbilled receivables attributable to revenue recognized during each of the three months ended March 31, 2019 and 2018 was less than $0.1 million . The change in contract assets attributable to revenue recognized during the three months ended March 31, 2019 and 2018 was $0.8 million and less than $0.1 million , respectively. Accounting Standards Updates In January 2017, the FASB issued guidance on accounting for goodwill impairments. The guidance eliminates Step 2 from the goodwill impairment test and requires, among other things, recognition of an impairment loss when the carrying value of a reporting unit exceeds its fair value. The loss recognized is limited to the total amount of goodwill allocated to that reporting unit. The guidance is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company does not expect the adoption of this guidance to have a material impact on the Company’s financial statements.

PREPAID AND OTHER CURRENT ASSET

PREPAID AND OTHER CURRENT ASSETS	3 Months Ended
	Mar. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
PREPAID AND OTHER CURRENT ASSETS	PREPAID AND OTHER CURRENT ASSETS Prepaid and other current assets consisted of the following: As of March 31, 2019 December 31, 2018 Unbilled receivables $ 131.3 $ 126.1 Prepaid income tax 102.2 125.1 Value added tax and other consumption tax receivables 85.1 86.3 Prepaid assets 54.0 40.5 Prepaid operating ground leases — 165.0 Other miscellaneous current assets 98.6 78.2 Prepaids and other current assets $ 471.2 $ 621.2 The reduction in Prepaid operating ground leases is a result of the reclassification of assets to the Right-of-use asset in connection with the Company’s adoption of the new lease accounting standard.

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT	PROPERTY AND EQUIPMENT Property and equipment (including assets held under financing leases) consisted of the following: Estimated Useful Lives (years) (1) As of March 31, 2019 December 31, 2018 Towers Up to 20 $ 12,850.9 $ 12,777.9 Equipment (2) 2 - 20 1,700.7 1,667.3 Buildings and improvements 3 - 32 632.6 628.5 Land and improvements (3) Up to 20 2,318.3 2,285.4 Construction-in-progress 364.8 358.1 Total 17,867.3 17,717.2 Less accumulated depreciation (6,664.7 ) (6,470.1 ) Property and equipment, net $ 11,202.6 $ 11,247.1 _______________ (1) Assets on leased land are depreciated over the shorter of the estimated useful life of the asset or the term of the corresponding ground lease taking into consideration lease renewal options and residual value. (2) Includes fiber and DAS assets. (3) Estimated useful lives apply to improvements only. Depreciation expense for the three months ended March 31, 2019 and 2018 was $223.7 million and $222.5 million , respectively. Included in depreciation expense for the three months ended March 31, 2019 was $42.4 million related to finance lease assets. As of December 31, 2018, property and equipment included $4,369.5 million of capital lease assets with related equipment and improvements and $1,016.2 million of accumulated depreciation. Information about finance lease-related balances is as follows: As of Finance leases: Classification March 31, 2019 Property and equipment Towers $ 2,780.9 Accumulated depreciation (1,042.6 ) Property and equipment, net 1,738.3 Property and equipment Buildings and improvements $ 171.1 Accumulated depreciation (60.4 ) Property and equipment, net $ 110.7 Property and equipment Land $ 130.3 Property and equipment Equipment $ 38.1 Accumulated depreciation (9.6 ) Property and equipment, net $ 28.5 As of March 31, 2019, the Company had $1,458.1 million of perpetual land easements which are not depreciable.

LEASES

LEASES	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
LEASES	LEASES -50-3, 842-20-50-9] The Company determines if an arrangement is a lease at the inception of the agreement. The Company determines an arrangement is a lease if it conveys the right to control the use of the communications site or ground space underneath a communications site for a period of time in exchange for consideration. The Company is both a lessor and a lessee. Lessor —The Company is a lessor in most of its revenue arrangements, as property revenue is derived from tenant leases of specifically-identified, physically distinct space on the Company’s communications real estate assets. The Company’s lease arrangements with its tenants vary depending upon the region and the industry of the tenant and generally have initial non-cancellable terms of five to ten years with multiple renewal terms. The leases also contain provisions that periodically increase the rent due, typically annually, based on a fixed escalation percentage or an inflationary index, or a combination of both. The Company structures its leases to include financial penalties if a tenant terminates the lease, which serve to disincentivize tenants from terminating the lease prior to the expiration of the lease term. The Company’s leasing arrangements outside of the U.S. may require that the Company provide power to the communications site through an electrical grid connection, diesel fuel generators or other sources and permit the Company to pass through the costs of, or otherwise charge for, these services. Many arrangements require that the communications site has power for a specified percentage of time. In most cases, if delivery of power falls below the specified service level, a corresponding reduction in revenue is recorded. The Company has determined that this performance obligation is satisfied over time for the duration of the lease. The Company typically has more than one tenant on a site and, by performing repair and maintenance work, can often lease a site, either through renewing existing agreements or leasing to new tenants, for periods beyond the existing tenant lease term. Accordingly, the Company has minimal risk with respect to the residual value of its leased assets. Communications sites are depreciated over their estimated useful lives, which generally does not exceed twenty years. As of March 31, 2019, the Company does not have any material related party leases as a lessor. The Company generally does not enter into sales-type leases or direct financing leases. The Company’s leases generally do not include any incentives for the lessee and do not include any lessee purchase options. The Company assesses its right-of-use asset and other lease-related assets for impairment, as described in note 1 to the Company’s consolidated financial statements included in the 2018 Form 10-K. As of March 31, 2019, there was no impairment recorded related to these assets. Historically, the Company has been able to successfully renew its ground leases as needed to ensure its tower revenue. Accordingly, the Company assumes that it will have access to the land underneath its tower sites when calculating future minimum rental receipts. Future minimum rental receipts expected under non-cancellable operating lease agreements as of March 31, 2019 were as follows: Fiscal Year Amount (1) Remainder of 2019 $ 3,987.3 2020 5,143.4 2021 4,739.9 2022 3,821.5 2023 3,516.4 Thereafter 13,254.4 Total $ 34,462.9 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Future minimum rental receipts expected under non-cancellable operating lease agreements in effect at December 31, 2018 were as follows: Year Ended December 31, Amount (1) 2019 $ 5,251.2 2020 5,062.2 2021 4,676.1 2022 3,754.6 2023 3,457.3 Thereafter 12,641.1 Total $ 34,842.5 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Lessee —The Company enters into arrangements as a lessee primarily for ground space underneath its communications sites. These arrangements are typically long-term lease agreements with initial non-cancellable terms of approximately five to ten years with one or more automatic or exercisable renewal periods and specified increases in lease payments upon exercise of the renewal options. The Company typically exercises its ground lease renewal options in order to provide ongoing tenant space on its communications sites through the end of the tenant lease term. Escalation clauses present in operating leases, excluding those tied to a consumer price index (“CPI”) or other inflation-based indices, are recognized on a straight-line basis over the estimated lease term of the applicable lease. Additionally, the escalations tied to CPI or another inflation-based index are considered variable lease payments. In certain circumstances, the Company enters into revenue sharing arrangements with the ground space owner, which results in variability in lease payments. In most markets outside of the U.S., in the event there are no tenants on the communications site, the Company generally has unilateral termination rights and in certain situations, the lease is structured to allow for termination by the Company with minimal or no penalties. Ground lease arrangements usually include annual escalations and do not contain any residual value guarantees or restrictions on dividends, other financial obligations or other similar terms. The Company has entered into certain transactions whereby at the end of a lease, sublease or similar arrangement, the Company has the option to purchase the corresponding communications sites. These transactions are further described in note 15 . The Company’s lease liability is the present value of the remaining minimum rental payments to be made over the remaining lease term, including renewal options reasonably certain to be exercised. The Company also considers termination options and factors those into the determination of lease payments when appropriate. To determine the lease term, the Company considers all renewal periods that are reasonably certain to be exercised, taking into consideration all economic factors, including the communications site’s estimated economic life (generally 20 years) and the respective lease terms of the Company’s tenants under the existing lease arrangements on such site. As of the adoption date and new lease inception, the Company’s right-of-use asset is equal to its lease liability, plus payments made prior to the commencement date and initial direct costs, net of any impairment losses, lease incentives, fair value adjustments on acquired leases and deferred rent amount recorded under the prior lease accounting guidance. As of March 31, 2019 , the Company does not have any material related party leases as a lessee. The Company does not have any sale-leaseback arrangements as lessee and typically does not enter into leveraged leases. The Company leases certain land and office space under operating leases and land and improvements, towers and vehicles under finance leases. As of March 31, 2019 , operating lease assets were included in Right-of-use asset and finance lease assets were included in Property and equipment, net in the consolidated balance sheet. Information about other lease-related balances as of March 31, 2019 is as follows: Operating leases: Right-of-use asset $ 7,080.9 Current portion of lease liabilities $ 498.4 Lease liabilities 6,316.1 Total operating lease liabilities $ 6,814.5 Finance leases: Current portion of lease liabilities $ 6.5 Lease liabilities 21.8 Total finance lease liabilities $ 28.3 As most of the Company’s leases do not specifically state an implicit rate, the Company uses a market-specific incremental borrowing rate consistent with the lease term as of the lease commencement date when calculating the present value of remaining lease payments. The incremental borrowing rate reflects the cost to borrow on a securitized basis in each market. The remaining lease term does not reflect all renewal options available to the Company, only those renewal options that the Company has assessed as reasonably certain taking into consideration the economic factors noted above. The weighted-average remaining lease terms and incremental borrowing rates as of March 31, 2019 are as follows: Operating leases: Weighted-average remaining lease term (years) 13.0 Weighted-average incremental borrowing rate 6.1 % Finance leases: Weighted-average remaining lease term (years) 9.2 Weighted-average incremental borrowing rate 6.0 % The following table sets forth the components of lease cost for the three months ended March 31, 2019 : Operating lease cost $ 255.0 Variable lease costs not included in lease liability (1) 52.3 Finance lease cost: Amortization of right-of-use asset $ 1.8 Interest on lease liabilities 0.4 Total finance lease cost $ 2.2 _______________ (1) Includes property tax paid on behalf of the landlord. Supplemental cash flow information for the three months ended March 31, 2019 is as follows: Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ (234.9 ) Operating cash flows from finance leases $ (0.3 ) Financing cash flows from finance leases $ (1.3 ) Non-cash items: New operating leases $ 62.1 Operating lease modifications and reassessments $ 30.1 As of March 31, 2019 , the Company does not have material operating or financing leases that have not yet commenced. Maturities of operating and finance lease liabilities as of March 31, 2019 were as follows: Fiscal Year Operating Lease (1) Finance Lease (1) Remainder of 2019 $ 658.0 $ 6.0 2020 870.7 6.8 2021 853.1 3.9 2022 813.3 3.3 2023 773.6 2.0 Thereafter 6,137.5 24.8 Total lease payments 10,106.2 46.8 Less amounts representing interest (3,291.7 ) (18.5 ) Total lease liabilities 6,814.5 28.3 Less current portion of lease liabilities (498.4 ) (6.5 ) Non-current lease liabilities $ 6,316.1 $ 21.8 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Future minimum rental payments under non-cancellable operating leases as of December 31, 2018 is as follows: Year Ended December 31, Amount (1) 2019 $ 926.0 2020 904.2 2021 879.8 2022 834.2 2023 792.6 Thereafter 6,173.1 Total $ 10,509.9 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Future minimum rental payments under capital leases in effect as of December 31, 2018 were as follows: Year Ended December 31, Amount (1) 2019 $ 40.7 2020 32.7 2021 27.8 2022 23.7 2023 19.2 Thereafter 117.5 Total 261.6 Less amounts representing interest (82.1 ) Present value of capital lease obligations $ 179.5 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Included in the future minimum rental payments under capital leases and amounts representing interest as of December 31, 2018 were $220.3 million and $69.3 million , respectively, related to perpetual land easements, which are not accounted for as finance leases under the new lease accounting standard.
LEASES	LEASES -50-3, 842-20-50-9] The Company determines if an arrangement is a lease at the inception of the agreement. The Company determines an arrangement is a lease if it conveys the right to control the use of the communications site or ground space underneath a communications site for a period of time in exchange for consideration. The Company is both a lessor and a lessee. Lessor —The Company is a lessor in most of its revenue arrangements, as property revenue is derived from tenant leases of specifically-identified, physically distinct space on the Company’s communications real estate assets. The Company’s lease arrangements with its tenants vary depending upon the region and the industry of the tenant and generally have initial non-cancellable terms of five to ten years with multiple renewal terms. The leases also contain provisions that periodically increase the rent due, typically annually, based on a fixed escalation percentage or an inflationary index, or a combination of both. The Company structures its leases to include financial penalties if a tenant terminates the lease, which serve to disincentivize tenants from terminating the lease prior to the expiration of the lease term. The Company’s leasing arrangements outside of the U.S. may require that the Company provide power to the communications site through an electrical grid connection, diesel fuel generators or other sources and permit the Company to pass through the costs of, or otherwise charge for, these services. Many arrangements require that the communications site has power for a specified percentage of time. In most cases, if delivery of power falls below the specified service level, a corresponding reduction in revenue is recorded. The Company has determined that this performance obligation is satisfied over time for the duration of the lease. The Company typically has more than one tenant on a site and, by performing repair and maintenance work, can often lease a site, either through renewing existing agreements or leasing to new tenants, for periods beyond the existing tenant lease term. Accordingly, the Company has minimal risk with respect to the residual value of its leased assets. Communications sites are depreciated over their estimated useful lives, which generally does not exceed twenty years. As of March 31, 2019, the Company does not have any material related party leases as a lessor. The Company generally does not enter into sales-type leases or direct financing leases. The Company’s leases generally do not include any incentives for the lessee and do not include any lessee purchase options. The Company assesses its right-of-use asset and other lease-related assets for impairment, as described in note 1 to the Company’s consolidated financial statements included in the 2018 Form 10-K. As of March 31, 2019, there was no impairment recorded related to these assets. Historically, the Company has been able to successfully renew its ground leases as needed to ensure its tower revenue. Accordingly, the Company assumes that it will have access to the land underneath its tower sites when calculating future minimum rental receipts. Future minimum rental receipts expected under non-cancellable operating lease agreements as of March 31, 2019 were as follows: Fiscal Year Amount (1) Remainder of 2019 $ 3,987.3 2020 5,143.4 2021 4,739.9 2022 3,821.5 2023 3,516.4 Thereafter 13,254.4 Total $ 34,462.9 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Future minimum rental receipts expected under non-cancellable operating lease agreements in effect at December 31, 2018 were as follows: Year Ended December 31, Amount (1) 2019 $ 5,251.2 2020 5,062.2 2021 4,676.1 2022 3,754.6 2023 3,457.3 Thereafter 12,641.1 Total $ 34,842.5 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Lessee —The Company enters into arrangements as a lessee primarily for ground space underneath its communications sites. These arrangements are typically long-term lease agreements with initial non-cancellable terms of approximately five to ten years with one or more automatic or exercisable renewal periods and specified increases in lease payments upon exercise of the renewal options. The Company typically exercises its ground lease renewal options in order to provide ongoing tenant space on its communications sites through the end of the tenant lease term. Escalation clauses present in operating leases, excluding those tied to a consumer price index (“CPI”) or other inflation-based indices, are recognized on a straight-line basis over the estimated lease term of the applicable lease. Additionally, the escalations tied to CPI or another inflation-based index are considered variable lease payments. In certain circumstances, the Company enters into revenue sharing arrangements with the ground space owner, which results in variability in lease payments. In most markets outside of the U.S., in the event there are no tenants on the communications site, the Company generally has unilateral termination rights and in certain situations, the lease is structured to allow for termination by the Company with minimal or no penalties. Ground lease arrangements usually include annual escalations and do not contain any residual value guarantees or restrictions on dividends, other financial obligations or other similar terms. The Company has entered into certain transactions whereby at the end of a lease, sublease or similar arrangement, the Company has the option to purchase the corresponding communications sites. These transactions are further described in note 15 . The Company’s lease liability is the present value of the remaining minimum rental payments to be made over the remaining lease term, including renewal options reasonably certain to be exercised. The Company also considers termination options and factors those into the determination of lease payments when appropriate. To determine the lease term, the Company considers all renewal periods that are reasonably certain to be exercised, taking into consideration all economic factors, including the communications site’s estimated economic life (generally 20 years) and the respective lease terms of the Company’s tenants under the existing lease arrangements on such site. As of the adoption date and new lease inception, the Company’s right-of-use asset is equal to its lease liability, plus payments made prior to the commencement date and initial direct costs, net of any impairment losses, lease incentives, fair value adjustments on acquired leases and deferred rent amount recorded under the prior lease accounting guidance. As of March 31, 2019 , the Company does not have any material related party leases as a lessee. The Company does not have any sale-leaseback arrangements as lessee and typically does not enter into leveraged leases. The Company leases certain land and office space under operating leases and land and improvements, towers and vehicles under finance leases. As of March 31, 2019 , operating lease assets were included in Right-of-use asset and finance lease assets were included in Property and equipment, net in the consolidated balance sheet. Information about other lease-related balances as of March 31, 2019 is as follows: Operating leases: Right-of-use asset $ 7,080.9 Current portion of lease liabilities $ 498.4 Lease liabilities 6,316.1 Total operating lease liabilities $ 6,814.5 Finance leases: Current portion of lease liabilities $ 6.5 Lease liabilities 21.8 Total finance lease liabilities $ 28.3 As most of the Company’s leases do not specifically state an implicit rate, the Company uses a market-specific incremental borrowing rate consistent with the lease term as of the lease commencement date when calculating the present value of remaining lease payments. The incremental borrowing rate reflects the cost to borrow on a securitized basis in each market. The remaining lease term does not reflect all renewal options available to the Company, only those renewal options that the Company has assessed as reasonably certain taking into consideration the economic factors noted above. The weighted-average remaining lease terms and incremental borrowing rates as of March 31, 2019 are as follows: Operating leases: Weighted-average remaining lease term (years) 13.0 Weighted-average incremental borrowing rate 6.1 % Finance leases: Weighted-average remaining lease term (years) 9.2 Weighted-average incremental borrowing rate 6.0 % The following table sets forth the components of lease cost for the three months ended March 31, 2019 : Operating lease cost $ 255.0 Variable lease costs not included in lease liability (1) 52.3 Finance lease cost: Amortization of right-of-use asset $ 1.8 Interest on lease liabilities 0.4 Total finance lease cost $ 2.2 _______________ (1) Includes property tax paid on behalf of the landlord. Supplemental cash flow information for the three months ended March 31, 2019 is as follows: Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ (234.9 ) Operating cash flows from finance leases $ (0.3 ) Financing cash flows from finance leases $ (1.3 ) Non-cash items: New operating leases $ 62.1 Operating lease modifications and reassessments $ 30.1 As of March 31, 2019 , the Company does not have material operating or financing leases that have not yet commenced. Maturities of operating and finance lease liabilities as of March 31, 2019 were as follows: Fiscal Year Operating Lease (1) Finance Lease (1) Remainder of 2019 $ 658.0 $ 6.0 2020 870.7 6.8 2021 853.1 3.9 2022 813.3 3.3 2023 773.6 2.0 Thereafter 6,137.5 24.8 Total lease payments 10,106.2 46.8 Less amounts representing interest (3,291.7 ) (18.5 ) Total lease liabilities 6,814.5 28.3 Less current portion of lease liabilities (498.4 ) (6.5 ) Non-current lease liabilities $ 6,316.1 $ 21.8 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Future minimum rental payments under non-cancellable operating leases as of December 31, 2018 is as follows: Year Ended December 31, Amount (1) 2019 $ 926.0 2020 904.2 2021 879.8 2022 834.2 2023 792.6 Thereafter 6,173.1 Total $ 10,509.9 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Future minimum rental payments under capital leases in effect as of December 31, 2018 were as follows: Year Ended December 31, Amount (1) 2019 $ 40.7 2020 32.7 2021 27.8 2022 23.7 2023 19.2 Thereafter 117.5 Total 261.6 Less amounts representing interest (82.1 ) Present value of capital lease obligations $ 179.5 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Included in the future minimum rental payments under capital leases and amounts representing interest as of December 31, 2018 were $220.3 million and $69.3 million , respectively, related to perpetual land easements, which are not accounted for as finance leases under the new lease accounting standard.
LEASES	LEASES -50-3, 842-20-50-9] The Company determines if an arrangement is a lease at the inception of the agreement. The Company determines an arrangement is a lease if it conveys the right to control the use of the communications site or ground space underneath a communications site for a period of time in exchange for consideration. The Company is both a lessor and a lessee. Lessor —The Company is a lessor in most of its revenue arrangements, as property revenue is derived from tenant leases of specifically-identified, physically distinct space on the Company’s communications real estate assets. The Company’s lease arrangements with its tenants vary depending upon the region and the industry of the tenant and generally have initial non-cancellable terms of five to ten years with multiple renewal terms. The leases also contain provisions that periodically increase the rent due, typically annually, based on a fixed escalation percentage or an inflationary index, or a combination of both. The Company structures its leases to include financial penalties if a tenant terminates the lease, which serve to disincentivize tenants from terminating the lease prior to the expiration of the lease term. The Company’s leasing arrangements outside of the U.S. may require that the Company provide power to the communications site through an electrical grid connection, diesel fuel generators or other sources and permit the Company to pass through the costs of, or otherwise charge for, these services. Many arrangements require that the communications site has power for a specified percentage of time. In most cases, if delivery of power falls below the specified service level, a corresponding reduction in revenue is recorded. The Company has determined that this performance obligation is satisfied over time for the duration of the lease. The Company typically has more than one tenant on a site and, by performing repair and maintenance work, can often lease a site, either through renewing existing agreements or leasing to new tenants, for periods beyond the existing tenant lease term. Accordingly, the Company has minimal risk with respect to the residual value of its leased assets. Communications sites are depreciated over their estimated useful lives, which generally does not exceed twenty years. As of March 31, 2019, the Company does not have any material related party leases as a lessor. The Company generally does not enter into sales-type leases or direct financing leases. The Company’s leases generally do not include any incentives for the lessee and do not include any lessee purchase options. The Company assesses its right-of-use asset and other lease-related assets for impairment, as described in note 1 to the Company’s consolidated financial statements included in the 2018 Form 10-K. As of March 31, 2019, there was no impairment recorded related to these assets. Historically, the Company has been able to successfully renew its ground leases as needed to ensure its tower revenue. Accordingly, the Company assumes that it will have access to the land underneath its tower sites when calculating future minimum rental receipts. Future minimum rental receipts expected under non-cancellable operating lease agreements as of March 31, 2019 were as follows: Fiscal Year Amount (1) Remainder of 2019 $ 3,987.3 2020 5,143.4 2021 4,739.9 2022 3,821.5 2023 3,516.4 Thereafter 13,254.4 Total $ 34,462.9 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Future minimum rental receipts expected under non-cancellable operating lease agreements in effect at December 31, 2018 were as follows: Year Ended December 31, Amount (1) 2019 $ 5,251.2 2020 5,062.2 2021 4,676.1 2022 3,754.6 2023 3,457.3 Thereafter 12,641.1 Total $ 34,842.5 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Lessee —The Company enters into arrangements as a lessee primarily for ground space underneath its communications sites. These arrangements are typically long-term lease agreements with initial non-cancellable terms of approximately five to ten years with one or more automatic or exercisable renewal periods and specified increases in lease payments upon exercise of the renewal options. The Company typically exercises its ground lease renewal options in order to provide ongoing tenant space on its communications sites through the end of the tenant lease term. Escalation clauses present in operating leases, excluding those tied to a consumer price index (“CPI”) or other inflation-based indices, are recognized on a straight-line basis over the estimated lease term of the applicable lease. Additionally, the escalations tied to CPI or another inflation-based index are considered variable lease payments. In certain circumstances, the Company enters into revenue sharing arrangements with the ground space owner, which results in variability in lease payments. In most markets outside of the U.S., in the event there are no tenants on the communications site, the Company generally has unilateral termination rights and in certain situations, the lease is structured to allow for termination by the Company with minimal or no penalties. Ground lease arrangements usually include annual escalations and do not contain any residual value guarantees or restrictions on dividends, other financial obligations or other similar terms. The Company has entered into certain transactions whereby at the end of a lease, sublease or similar arrangement, the Company has the option to purchase the corresponding communications sites. These transactions are further described in note 15 . The Company’s lease liability is the present value of the remaining minimum rental payments to be made over the remaining lease term, including renewal options reasonably certain to be exercised. The Company also considers termination options and factors those into the determination of lease payments when appropriate. To determine the lease term, the Company considers all renewal periods that are reasonably certain to be exercised, taking into consideration all economic factors, including the communications site’s estimated economic life (generally 20 years) and the respective lease terms of the Company’s tenants under the existing lease arrangements on such site. As of the adoption date and new lease inception, the Company’s right-of-use asset is equal to its lease liability, plus payments made prior to the commencement date and initial direct costs, net of any impairment losses, lease incentives, fair value adjustments on acquired leases and deferred rent amount recorded under the prior lease accounting guidance. As of March 31, 2019 , the Company does not have any material related party leases as a lessee. The Company does not have any sale-leaseback arrangements as lessee and typically does not enter into leveraged leases. The Company leases certain land and office space under operating leases and land and improvements, towers and vehicles under finance leases. As of March 31, 2019 , operating lease assets were included in Right-of-use asset and finance lease assets were included in Property and equipment, net in the consolidated balance sheet. Information about other lease-related balances as of March 31, 2019 is as follows: Operating leases: Right-of-use asset $ 7,080.9 Current portion of lease liabilities $ 498.4 Lease liabilities 6,316.1 Total operating lease liabilities $ 6,814.5 Finance leases: Current portion of lease liabilities $ 6.5 Lease liabilities 21.8 Total finance lease liabilities $ 28.3 As most of the Company’s leases do not specifically state an implicit rate, the Company uses a market-specific incremental borrowing rate consistent with the lease term as of the lease commencement date when calculating the present value of remaining lease payments. The incremental borrowing rate reflects the cost to borrow on a securitized basis in each market. The remaining lease term does not reflect all renewal options available to the Company, only those renewal options that the Company has assessed as reasonably certain taking into consideration the economic factors noted above. The weighted-average remaining lease terms and incremental borrowing rates as of March 31, 2019 are as follows: Operating leases: Weighted-average remaining lease term (years) 13.0 Weighted-average incremental borrowing rate 6.1 % Finance leases: Weighted-average remaining lease term (years) 9.2 Weighted-average incremental borrowing rate 6.0 % The following table sets forth the components of lease cost for the three months ended March 31, 2019 : Operating lease cost $ 255.0 Variable lease costs not included in lease liability (1) 52.3 Finance lease cost: Amortization of right-of-use asset $ 1.8 Interest on lease liabilities 0.4 Total finance lease cost $ 2.2 _______________ (1) Includes property tax paid on behalf of the landlord. Supplemental cash flow information for the three months ended March 31, 2019 is as follows: Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ (234.9 ) Operating cash flows from finance leases $ (0.3 ) Financing cash flows from finance leases $ (1.3 ) Non-cash items: New operating leases $ 62.1 Operating lease modifications and reassessments $ 30.1 As of March 31, 2019 , the Company does not have material operating or financing leases that have not yet commenced. Maturities of operating and finance lease liabilities as of March 31, 2019 were as follows: Fiscal Year Operating Lease (1) Finance Lease (1) Remainder of 2019 $ 658.0 $ 6.0 2020 870.7 6.8 2021 853.1 3.9 2022 813.3 3.3 2023 773.6 2.0 Thereafter 6,137.5 24.8 Total lease payments 10,106.2 46.8 Less amounts representing interest (3,291.7 ) (18.5 ) Total lease liabilities 6,814.5 28.3 Less current portion of lease liabilities (498.4 ) (6.5 ) Non-current lease liabilities $ 6,316.1 $ 21.8 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Future minimum rental payments under non-cancellable operating leases as of December 31, 2018 is as follows: Year Ended December 31, Amount (1) 2019 $ 926.0 2020 904.2 2021 879.8 2022 834.2 2023 792.6 Thereafter 6,173.1 Total $ 10,509.9 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Future minimum rental payments under capital leases in effect as of December 31, 2018 were as follows: Year Ended December 31, Amount (1) 2019 $ 40.7 2020 32.7 2021 27.8 2022 23.7 2023 19.2 Thereafter 117.5 Total 261.6 Less amounts representing interest (82.1 ) Present value of capital lease obligations $ 179.5 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Included in the future minimum rental payments under capital leases and amounts representing interest as of December 31, 2018 were $220.3 million and $69.3 million , respectively, related to perpetual land easements, which are not accounted for as finance leases under the new lease accounting standard.

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS	GOODWILL AND OTHER INTANGIBLE ASSETS The changes in the carrying value of goodwill for each of the Company’s business segments were as follows: Property Services Total U.S. Asia EMEA Latin America Balance as of January 1, 2019 $ 3,382.5 $ 1,045.5 $ 381.3 $ 690.6 $ 2.0 $ 5,501.9 Additions and adjustments (1) 30.1 — — — — 30.1 Effect of foreign currency translation — 9.2 (6.8 ) 3.8 — 6.2 Balance as of March 31, 2019 $ 3,412.6 $ 1,054.7 $ 374.5 $ 694.4 $ 2.0 $ 5,538.2 _______________ (1) Additions consist of $30.9 million resulting from 2019 acquisitions offset by $0.8 million from revisions to prior-year acquisitions due to measurement period adjustments. The Company’s other intangible assets subject to amortization consisted of the following: As of March 31, 2019 As of December 31, 2018 Estimated Useful Gross Carrying Value Accumulated Amortization Net Book Value Gross Carrying Value Accumulated Amortization Net Book Value Acquired network location intangibles (1) Up to 20 $ 4,780.2 $ (1,762.3 ) $ 3,017.9 $ 4,780.3 $ (1,704.9 ) $ 3,075.4 Acquired tenant-related intangibles 15-20 11,212.8 (3,278.0 ) 7,934.8 11,156.5 (3,147.2 ) 8,009.3 Acquired licenses and other intangibles 3-20 105.3 (15.2 ) 90.1 104.1 (14.5 ) 89.6 Total other intangible assets $ 16,098.3 $ (5,055.5 ) $ 11,042.8 $ 16,040.9 $ (4,866.6 ) $ 11,174.3 _______________ (1) Acquired network location intangibles are amortized over the shorter of the term of the corresponding ground lease, taking into consideration lease renewal options and residual value, or up to 20 years, as the Company considers these intangibles to be directly related to the tower assets. The acquired network location intangibles represent the value to the Company of the incremental revenue growth that could potentially be obtained from leasing the excess capacity on acquired communications sites. The acquired tenant-related intangibles typically represent the value to the Company of tenant contracts and relationships in place at the time of an acquisition or similar transaction, including assumptions regarding estimated renewals. The Company amortizes its acquired network location intangibles and tenant-related intangibles on a straight-line basis over their estimated useful lives. As of March 31, 2019 , the remaining weighted average amortization period of the Company’s intangible assets was 14 years. Amortization of intangible assets for the three months ended March 31, 2019 and 2018 was $192.7 million and $202.4 million , respectively. Based on current exchange rates, the Company expects to record amortization expense as follows over the remaining current year and the five subsequent years: Fiscal Year Amount Remainder of 2019 $ 586.7 2020 763.4 2021 746.9 2022 742.5 2023 738.2 2024 734.9

NOTES RECEIVABLE AND OTHER NON-

NOTES RECEIVABLE AND OTHER NON-CURRENT ASSETS	3 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
NOTES RECEIVABLE AND OTHER NON-CURRENT ASSETS	NOTES RECEIVABLE AND OTHER NON-CURRENT ASSETS Notes receivable and other non-current assets consisted of the following: As of March 31, 2019 December 31, 2018 Long-term prepaid ground rent — 607.5 Notes receivable 0.9 1.0 Other miscellaneous assets 278.2 354.1 Notes receivable and other non-current assets $ 279.1 $ 962.6 The reduction in Long-term prepaid ground rent is a result of the reclassification of assets to the Right-of-use asset in connection with the Company’s adoption of the new lease accounting standard.

ACCRUED EXPENSES

ACCRUED EXPENSES	3 Months Ended
	Mar. 31, 2019
Payables and Accruals [Abstract]
ACCRUED EXPENSES	ACCRUED EXPENSES Accrued expenses consisted of the following: As of March 31, 2019 December 31, 2018 Accrued property and real estate taxes $ 177.1 $ 169.7 Accrued pass-through costs 80.1 71.2 Amounts payable to tenants 78.2 93.5 Accrued rent 69.6 61.4 Payroll and related withholdings 60.5 90.4 Accrued construction costs 28.1 41.5 Accrued income tax payable 23.3 57.9 Accrued pass-through taxes 9.5 2.2 Other accrued expenses 337.3 360.5 Total accrued expenses $ 863.7 $ 948.3

LONG-TERM OBLIGATIONS

LONG-TERM OBLIGATIONS	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
LONG-TERM OBLIGATIONS	LONG-TERM OBLIGATIONS Outstanding amounts under the Company’s long-term obligations, reflecting discounts, premiums, debt issuance costs and fair value adjustments due to interest rate swaps consisted of the following: As of March 31, 2019 December 31, 2018 Maturity Date 2018 Term Loan (1) (2) $ — $ 1,499.8 March 29, 2019 2019 Term Loan (1) 1,299.4 — February 13, 2020 2013 Credit Facility (1) 2,340.0 1,875.0 June 28, 2022 2013 Term Loan (1) 995.0 994.8 January 31, 2024 2014 Credit Facility (1) — — January 31, 2024 3.40% senior notes (3) — 1,000.0 February 15, 2019 2.800% senior notes 748.2 747.8 June 1, 2020 5.050% senior notes (4) 698.9 698.7 September 1, 2020 3.300% senior notes 747.5 747.2 February 15, 2021 3.450% senior notes 646.7 646.3 September 15, 2021 5.900% senior notes 498.5 498.4 November 1, 2021 2.250% senior notes 578.9 572.7 January 15, 2022 4.70% senior notes 697.6 697.4 March 15, 2022 3.50% senior notes 993.0 992.6 January 31, 2023 3.000% senior notes 694.1 687.5 June 15, 2023 5.00% senior notes 1,002.2 1,002.1 February 15, 2024 3.375% senior notes 643.5 — May 15, 2024 1.375% senior notes 552.2 564.0 April 4, 2025 4.000% senior notes 742.3 742.1 June 1, 2025 4.400% senior notes 496.2 496.1 February 15, 2026 1.950% senior notes 554.0 566.0 May 22, 2026 3.375% senior notes 986.7 986.3 October 15, 2026 3.125% senior notes 397.4 397.3 January 15, 2027 3.55% senior notes 743.6 743.5 July 15, 2027 3.600% senior notes 692.1 691.9 January 15, 2028 3.950% senior notes 588.9 — March 15, 2029 Total American Tower Corporation debt 18,336.9 17,847.5 Series 2013-2A securities (5) 1,293.8 1,293.4 March 15, 2023 Series 2018-1A securities (5) 493.7 493.5 March 15, 2028 Series 2015-1 notes (6) 349.0 348.8 June 15, 2020 Series 2015-2 notes (7) 520.9 520.8 June 16, 2025 India indebtedness (8) — 240.1 Various India preference shares (9) — 23.9 March 2, 2020 Shareholder loan (10) 53.4 59.9 December 31, 2019 Other subsidiary debt (11) 128.3 152.5 Various Total American Tower subsidiary debt 2,839.1 3,132.9 Finance and capital lease obligations 28.3 179.5 Total 21,204.3 21,159.9 Less current portion of long-term obligations (2,097.2 ) (2,754.8 ) Long-term obligations $ 19,107.1 $ 18,405.1 _______________ (1) Accrues interest at a variable rate. (2) Repaid in full on February 14, 2019 using proceeds from the 2019 Term Loan (as defined below) and cash on hand. (3) Repaid in full on the maturity date in February 2019 with borrowings from the 2013 Credit Facility and the 2014 Credit Facility (each defined below). (4) Repaid in full on April 22, 2019 with borrowings from the 2014 Credit Facility and cash on hand. (5) Maturity date reflects the anticipated repayment date; final legal maturity is March 15, 2048. (6) Maturity date reflects the anticipated repayment date; final legal maturity is June 15, 2045. (7) Maturity date reflects the anticipated repayment date; final legal maturity is June 15, 2050. (8) Denominated in Indian Rupees (“INR”). Included India working capital facilities, remaining debt assumed by the Company in connection with the Viom Acquisition (as defined in note 12) and debt that has been entered into by ATC TIPL. During the three months ended March 31, 2019, the Company repaid all remaining debt assumed in connection with the Viom Acquisition and debt entered into by ATC TIPL. (9) Mandatorily redeemable preference shares (the “Preference Shares”) denominated in INR and classified as debt. The Preference Shares were redeemed on March 2, 2019. (10) Reflects balance owed to the Company’s joint venture partner in Ghana. The Ghana loan is denominated in Ghanaian Cedi (“GHS”). (11) Includes the South African credit facility, which is denominated in South African Rand and amortizes through December 17, 2020, the Colombian credit facility, which is denominated in Colombian Pesos and amortizes through April 24, 2021, the Brazil credit facility, which is denominated in Brazilian Reais and amortizes through January 15, 2022, the Kenya debt, which is denominated in U.S. Dollars (“USD”) and is payable either (i) in future installments subject to the satisfaction of specified conditions or (ii) three years from the note origination date, and U.S. subsidiary debt related to a seller-financed acquisition. Current portion of long-term obligations— The Company’s current portion of long-term obligations primarily includes (i) $1.3 billion under its unsecured term loan entered into on February 14, 2019 (the “2019 Term Loan”), (ii) $698.9 million under the 5.050% senior unsecured notes due 2020 (the “ 5.050% Notes”) and (iii) 294.4 million GHS ( $53.4 million ) of the shareholder loan owed to the Company’s joint venture partner in Ghana. Securitized Debt— Cash flows generated by the sites that secure the securitized debt of the Company are only available for payment of such debt and are not available to pay the Company’s other obligations or the claims of its creditors. However, subject to certain restrictions, the Company holds the right to receive the excess cash flows not needed to pay the securitized debt and other obligations arising out of the securitizations. The securitized debt is the obligation of the issuers thereof or borrowers thereunder, as applicable, and their subsidiaries, and not of the Company or its other subsidiaries. Senior Notes Repayment of 3.40% Senior Notes— On the February 15, 2019 maturity date, the Company repaid $1.0 billion aggregate principal amount of 3.40% senior unsecured notes due 2019 (the “ 3.40% Notes”). The 3.40% Notes were repaid with borrowings from the Company’s multicurrency senior unsecured revolving credit facility entered into in June 2013, as amended (the “2013 Credit Facility”) and the Company’s senior unsecured revolving credit facility entered into in January 2012 and amended and restated in September 2014, as further amended (the “2014 Credit Facility”). Upon completion of the repayment, none of the 3.40% Notes remain outstanding. 3.375% Senior Notes and 3.950% Senior Notes Offering— On March 15, 2019, the Company completed a registered public offering of $650.0 million aggregate principal amount of 3.375% senior unsecured notes due 2024 (the “ 3.375% Notes”) and $600.0 million aggregate principal amount of 3.950% senior unsecured notes due 2029 (the “ 3.950% Notes” and, collectively with the 3.375% Notes, the “Notes”). The net proceeds from this offering were approximately $1,231.0 million , after deducting commissions and estimated expenses. The Company used the net proceeds to repay existing indebtedness under the 2013 Credit Facility and 2014 Credit Facility. The 3.375% Notes will mature on May 15, 2024 and bear interest at a rate of 3.375% per annum. The 3.950% Notes will mature on March 15, 2029 and bear interest at a rate of 3.950% per annum. Accrued and unpaid interest on the 3.375% Notes will be payable in U.S. Dollars semi-annually in arrears on May 15 and November 15 of each year, beginning on November 15, 2019. Accrued and unpaid interest on the 3.950% Notes will be payable in U.S. Dollars semi-annually in arrears on March 15 and September 15 of each year, beginning on September 15, 2019. Interest on the Notes will accrue from March 15, 2019 and will be computed on the basis of a 360 -day year comprised of twelve 30-day months. The Company may redeem the Notes at any time, in whole or in part, at a redemption price equal to 100% of the principal amount of the Notes plus a make-whole premium, together with accrued interest to the redemption date. If the Company redeems the 3.375% Notes on or after April 15, 2024 or the 3.950% Notes on or after December 15, 2028, 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 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 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 3.5 x Adjusted EBITDA, as defined in the supplemental indenture. Bank Facilities 2013 Credit Facility— During the three months ended March 31, 2019 , the Company borrowed an aggregate of $995.0 million and repaid an aggregate of $530.0 million of revolving indebtedness under the 2013 Credit Facility. The Company used the borrowings to fund acquisitions, to purchase noncontrolling interests in its Indian subsidiary, ATC TIPL, to repay existing indebtedness and for general corporate purposes. 2014 Credit Facility— During the three months ended March 31, 2019 , the Company borrowed an aggregate of $705.0 million and repaid an aggregate of $705.0 million of revolving indebtedness under the 2014 Credit Facility. The Company used the borrowings to repay existing indebtedness and for general corporate purposes. 2019 Term Loan— During the three months ended March 31, 2019 , the Company entered into the 2019 Term Loan, the net proceeds of which were used, together with cash on hand, to repay all outstanding indebtedness under its unsecured term loan entered into on March 29, 2018. The 2019 Term Loan matures on February 13, 2020. Any outstanding principal and accrued but unpaid interest will be due and payable in full at maturity. The 2019 Term Loan may be paid prior to maturity in whole or in part at the Company’s option without penalty or premium. The 2019 Term Loan agreement contains certain reporting, information, financial and operating covenants and other restrictions (including limitations on additional debt, guaranties, sales of assets and liens) with which the Company must comply. Any failure to comply with the financial and operating covenants of the loan agreement may constitute a default, which could result in, among other things, the amounts outstanding, including all accrued interest and unpaid fees, becoming immediately due and payable. As of March 31, 2019 , the key terms under the 2013 Credit Facility, the 2014 Credit Facility, the Company’s unsecured term loan entered into in October 2013, as amended (the “2013 Term Loan”) and the 2019 Term Loan were as follows: Outstanding Principal Balance (in millions) Undrawn letters of credit (in millions) Maturity Date Current margin over LIBOR (1) Current commitment fee (2) 2013 Credit Facility $ 2,340.0 $ 3.8 June 28, 2022 (3) 1.125 % 0.125 % 2014 Credit Facility $ — $ 6.2 January 31, 2024 (3) 1.125 % 0.125 % 2013 Term Loan $ 1,000.0 N/A January 31, 2024 1.125 % N/A 2019 Term Loan $ 1,300.0 N/A February 13, 2020 0.800 % N/A _______________ (1) LIBOR means the London Interbank Offered Rate. (2) Fee on undrawn portion of each credit facility. (3) Subject to two optional renewal periods.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS The Company determines the fair value of its financial instruments based on the fair value hierarchy, which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. Below are the three levels of inputs that may be used to measure fair value: Level 1 Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2 Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Items Measured at Fair Value on a Recurring Basis —The fair values of the Company’s financial assets and liabilities that are required to be measured on a recurring basis at fair value were as follows: March 31, 2019 December 31, 2018 Fair Value Measurements Using Fair Value Measurements Using Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Assets: Short-term investments (1) — $ 18.4 — — — — Embedded derivative in lease agreement — — $ 11.3 — — $ 11.5 Liabilities: Interest rate swap agreements — $ 21.8 — — $ 33.8 — Acquisition-related contingent consideration — — $ 0.8 — — $ 0.9 Fair value of debt related to interest rate swap agreements (2) $ (19.0 ) — — $ (31.3 ) — — Redeemable noncontrolling interests — — $ 589.0 — — $ 1,004.8 _______________ (1) Consists of mutual funds with a portfolio duration of approximately 90 days. (2) Included in the carrying values of the corresponding debt obligations. As of March 31, 2019 , the Company had marketable securities with a cost basis of $18.1 million and recognized unrealized gains of $0.3 million on these securities. During the three months ended March 31, 2019 , the Company made no changes to the methods described in note 11 to its consolidated financial statements included in the 2018 Form 10-K that it used to measure the fair value of its interest rate swap agreements, the embedded derivative in one of its lease agreements, acquisition-related contingent consideration and redeemable noncontrolling interests. The changes in fair value for the embedded derivative in one of its lease agreements and acquisition-related contingent consideration during the three months ended March 31, 2019 and 2018 were not material to the consolidated financial statements. The changes in the carrying amount of the redeemable noncontrolling interests are described in note 12. As of March 31, 2019 , the Company estimated the value of all potential acquisition-related contingent consideration payments to be between zero and $0.8 million . Items Measured at Fair Value on a Nonrecurring Basis Assets Held and Used —The Company’s long-lived assets are recorded at amortized cost and, if impaired, are adjusted to fair value using Level 3 inputs. During the three months ended March 31, 2019 and 2018 , the Company recorded $18.1 million and $147.4 million of impairments, respectively. These impairments were recorded in Other operating expenses in the consolidated statements of operations. There were no other items measured at fair value on a nonrecurring basis during the three months ended March 31, 2019 or 2018 . Fair Value of Financial Instruments —The Company’s financial instruments for which the carrying value reasonably approximates fair value at March 31, 2019 and December 31, 2018 include cash and cash equivalents, restricted cash, accounts receivable and accounts payable. The Company’s estimates of fair value of its long-term obligations, including the current portion, are based primarily upon reported market values. For long-term debt not actively traded, fair value is estimated using either indicative price quotes or a discounted cash flow analysis using rates for debt with similar terms and maturities. As of March 31, 2019 and December 31, 2018 , the carrying value of long-term obligations, including the current portion, was $21.2 billion and $21.2 billion , respectively. As of March 31, 2019 , the fair value of long-term obligations, including the current portion, was $21.5 billion , of which $14.0 billion was measured using Level 1 inputs and $7.5 billion was measured using Level 2 inputs. As of December 31, 2018 , the fair value of long-term obligations, including the current portion, was $21.1 billion , of which $13.4 billion was measured using Level 1 inputs and $7.7 billion was measured using Level 2 inputs.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [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. Under the provisions of the Internal Revenue Code of 1986, as amended, the Company may deduct amounts distributed to stockholders against the income generated by its real estate investment trust (“REIT”) operations. The Company continues to be subject to income taxes on the income of its domestic taxable REIT subsidiaries and income taxes in foreign jurisdictions where it conducts operations. In addition, the Company is able to offset certain income by utilizing its net operating losses, subject to specified limitations. The Company provides valuation allowances if, based on the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. Management assesses the available evidence to estimate if sufficient future taxable income will be generated to use the existing deferred tax assets. The change in the Income tax (provision) benefit for the three months ended March 31, 2019 was primarily attributable to an increase in foreign earnings subject to taxation in the current period, as well as the nonrecurrence of events during the three months ended March 31, 2018 , including a one-time benefit for merger-related activity in the Company’s Asia property segment and the tax effect of certain impairment charges. As of March 31, 2019 and December 31, 2018 , the total unrecognized tax benefits that would impact the ETR, if recognized, were approximately $94.6 million and $93.7 million , respectively. The amount of unrecognized tax benefits during the three months ended March 31, 2019 includes additions to the Company’s existing tax positions of $1.5 million and foreign currency exchange rate fluctuations of $0.3 million . Unrecognized tax benefits are expected to change over the next 12 months if certain tax matters ultimately settle with the applicable taxing jurisdiction during this time frame, as described in note 12 to the Company’s consolidated financial statements included in the 2018 Form 10-K. The impact of the amount of these changes to previously recorded uncertain tax positions could range from zero to $2.8 million . The Company recorded the following penalties and income tax-related interest expense during the three months ended March 31, 2019 and 2018: Three Months Ended March 31, 2019 2018 Penalties and income tax-related interest expense $ 1.1 $ 1.0 As of March 31, 2019 and December 31, 2018 , the total amount of accrued income tax related interest and penalties included in the consolidated balance sheets were $20.3 million and $19.1 million , respectively.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION Summary of Stock-Based Compensation Plans —The Company maintains equity incentive plans that provide for the grant of stock-based awards to its directors, officers and employees. The 2007 Equity Incentive Plan, as amended (the “2007 Plan”), provides for the grant of non-qualified and incentive stock options, as well as restricted stock units, restricted stock and other stock-based awards. Exercise prices for non-qualified and incentive stock options are not less than the fair value of the underlying common stock on the date of grant. Equity awards typically vest ratably, generally over four years for time-based restricted stock units (“RSUs”) and stock options and three years for performance-based restricted stock units (“PSUs”). Stock options generally expire ten years from the date of grant. As of March 31, 2019 , the Company had the ability to grant stock-based awards with respect to an aggregate of 6.9 million shares of common stock under the 2007 Plan. In addition, the Company maintains an employee stock purchase plan (the “ESPP”) pursuant to which eligible employees may purchase shares of the Company’s common stock on the last day of each bi-annual offering period at a 15% discount from the lower of the closing market value on the first or last day of such offering period. The offering periods run from June 1 through November 30 and from December 1 through May 31 of each year. During the three months ended March 31, 2019 and 2018 , the Company recorded and capitalized the following stock-based compensation expense: Three Months Ended March 31, 2019 2018 Stock-based compensation expense Property $ 0.6 $ 0.7 Stock-based compensation expense Services 0.3 0.3 Stock-based compensation expense SG&A 41.6 41.7 Total stock-based compensation expense $ 42.5 $ 42.7 Stock-based compensation expense capitalized as property and equipment $ 0.5 $ 0.5 Stock Options —As of March 31, 2019 , total unrecognized compensation expense related to unvested stock options was $3.2 million , which is expected to be recognized over a weighted average period of approximately one year . The Company’s option activity for the three months ended March 31, 2019 was as follows (shares disclosed in full amounts): Number of Options Outstanding as of January 1, 2019 4,257,470 Granted — Exercised (314,847 ) Forfeited — Expired — Outstanding as of March 31, 2019 3,942,623 Restricted Stock Units— As of March 31, 2019 , total unrecognized compensation expense related to unvested RSUs granted under the 2007 Plan was $179.6 million and is expected to be recognized over a weighted average period of approximately three years . Vesting of RSUs is subject generally to the employee’s continued employment or death, disability or qualified retirement (each as defined in the applicable RSU award agreement). Performance-Based Restricted Stock Units— During the three months ended March 31, 2019 , 2018 and 2017, the Company’s Compensation Committee granted an aggregate of 114,823 PSUs (the “2019 PSUs”), 131,311 PSUs (the “2018 PSUs”) and 154,520 PSUs (the “2017 PSUs”), respectively, to its executive officers and established the performance metrics for these awards. Threshold, target and maximum parameters were established for the metrics for a three -year performance period with respect to each of the 2019 PSUs, 2018 PSUs and the 2017 PSUs and will be used to calculate the number of shares that will be issuable when each award vests, which may range from zero to 200% of the target amounts. At the end of each three -year performance period, the number of shares that vest will depend on the degree of achievement against the pre-established performance goals. PSUs will be paid out in common stock at the end of each performance period, subject generally to the executive’s continued employment or death, disability or qualified retirement (each as defined in the applicable PSU award agreement). PSUs will accrue dividend equivalents prior to vesting, which will be paid out only in respect of shares that actually vest. Restricted Stock Units and Performance-Based Restricted Stock Units —The Company’s RSU and PSU activity for the three months ended March 31, 2019 was as follows (shares disclosed in full amounts): RSUs PSUs Outstanding as of January 1, 2019 (1) 1,649,973 624,511 Granted (2) 539,905 114,823 Vested and Released (3) (607,845 ) (292,180 ) Forfeited (13,599 ) — Outstanding as of March 31, 2019 1,568,434 447,154 Vested and deferred as of March 31, 2019 (4) 32,596 46,500 _______________ (1) PSUs consist of the target number of shares issuable at the end of the three -year performance period for the 2018 PSUs and 2017 PSUs, or 131,311 and 154,520 shares, respectively, and the shares issuable at the end of the three -year performance period for the PSUs granted in 2016 (“2016 PSUs”) based on achievement against the performance metrics for the three-year performance period, or 338,680 shares. (2) PSUs consist of the target number of shares issuable at the end of the three -year performance period for the 2019 PSUs, or 114,823 shares. (3) PSUs consist of shares vested pursuant to the 2016 PSUs. There are no additional shares to be earned related to the 2016 PSUs. (4) Vested and deferred RSUs and PSUs are related to deferred compensation for certain former employees. During the three months ended March 31, 2019 , the Company recorded $10.7 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, 2019 was $20.4 million based on the Company’s current assessment of the probability of achieving the performance goals. The weighted average period over which the cost will be recognized is approximately two years .

REDEEMABLE NONCONTROLLING INTER

REDEEMABLE NONCONTROLLING INTERESTS	3 Months Ended
	Mar. 31, 2019
Noncontrolling Interest [Abstract]
REDEEMABLE NONCONTROLLING INTERESTS	REDEEMABLE NONCONTROLLING INTERESTS Redeemable Noncontrolling Interests —On April 21, 2016, the Company, through its wholly owned subsidiary, ATC Asia Pacific Pte. Ltd., acquired a 51% controlling ownership interest in ATC TIPL (formerly Viom), a telecommunications infrastructure company that owns and operates wireless communications towers and indoor DAS networks in India (the “Viom Acquisition”). In connection with the Viom Acquisition, the Company, through one of its subsidiaries, entered into a shareholders agreement (the “Shareholders Agreement”) with Viom and the following remaining Viom shareholders: Tata Sons Limited (“Tata Sons”), Tata Teleservices Limited (“Tata Teleservices”), IDFC Private Equity Fund III (“IDFC”), Macquarie SBI Infrastructure Investments Pte Limited and SBI Macquarie Infrastructure Trust (collectively, the “Remaining Shareholders”). The Shareholders Agreement also provides certain of the Remaining Shareholders with put options, which allow them to sell outstanding shares of ATC TIPL to the Company, and the Company with call options, which allow it to buy the noncontrolling shares of ATC TIPL. The put options, which are not under the Company’s control, cannot be separated from the noncontrolling interests. As a result, the combination of the noncontrolling interests and the redemption feature requires classification as redeemable noncontrolling interests in the consolidated balance sheet, separate from equity. 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 foreign currency translation adjustments, or (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 Net income attributable to noncontrolling interests. Due primarily to the impact of impairment charges on net income and, as a result, on the carrying value of the noncontrolling interests, the Company adjusted noncontrolling interests by $3.7 million and $17.5 million for the three months ended March 31, 2019 and 2018, respectively. The put options may be exercised, requiring the Company to purchase the Remaining Shareholders’ equity interests, on specified dates through March 31, 2021. The price of the put options will be based on the fair market value of the exercising Remaining Shareholders’ interest in the Company’s India operations at the time the option is exercised. Put options held by certain of the Remaining Shareholders are subject to a floor price of 216 INR per share. During the three months ended March 31, 2019 , the Company redeemed 50% of Tata Teleservices and Tata Sons’ combined holdings of ATC TIPL and 100% of IDFC’s holdings of ATC TIPL, for total consideration of INR 29.4 billion ( $425.7 million at the date of redemption). As a result of the redemption, the Company’s controlling interest in ATC TIPL increased from 63% to 79% and the noncontrolling interest decreased from 37% to 21% . The changes in Redeemable noncontrolling interests for the three months ended March 31, 2019 and 2018 were as follows: Three Months Ended March 31, 2019 2018 Balance as of January 1, $ 1,004.8 $ 1,126.2 Net loss attributable to noncontrolling interests (3.7 ) (28.1 ) Adjustment to noncontrolling interest redemption value 3.7 17.5 Adjustment to noncontrolling interest due to merger — (28.1 ) Purchase of noncontrolling interest (425.7 ) — Foreign currency translation adjustment attributable to noncontrolling interests 9.9 (22.3 ) Balance as of March 31, $ 589.0 $ 1,065.2

EQUITY

EQUITY	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
EQUITY	EQUITY Sales of Equity Securities —The Company receives proceeds from the sale of its equity securities pursuant to the ESPP and upon exercise of stock options granted under its equity incentive plan. During the three months ended March 31, 2019 , the Company received an aggregate of $27.2 million in proceeds upon exercises of stock options. Stock Repurchase Program —In March 2011, the Board of Directors approved a stock repurchase program, pursuant to which the Company is authorized to repurchase up to $1.5 billion of its common stock (the “2011 Buyback”). In December 2017, the Board of Directors approved an additional stock repurchase program, pursuant to which the Company is authorized to repurchase up to $2.0 billion of its common stock (the “2017 Buyback” and, together with the 2011 Buyback, the “Buyback Programs”). During the three months ended March 31, 2019 , there were no repurchases under either of the Buyback Programs. As of March 31, 2019 , the Company has repurchased a total of 14,003,543 shares of its common stock under the 2011 Buyback for an aggregate of $1.4 billion , including commissions and fees. The Company has not made any repurchases under the 2017 Buyback. Under the Buyback Programs, the Company is authorized to purchase shares from time to time through open market purchases, in privately negotiated transactions not to exceed market prices, and (with respect to such open market purchases) pursuant to plans adopted in accordance with Rule 10b5-1 under the Securities Exchange Act of 1934, as amended, in accordance with securities laws and other legal requirements and subject to market conditions and other factors. The Company expects to fund any further purchases of its common stock through a combination of cash on hand, cash generated by operations and borrowings under its credit facilities. Purchases under the Buyback Programs are subject to the Company having available cash to fund the purchases. Distributions —During the three months ended March 31, 2019 , the Company declared or paid the following cash distributions (per share data reflects actual amounts): Declaration Date Payment Date Record Date Distribution per share Aggregate Payment Amount (1) Common Stock March 7, 2019 April 26, 2019 April 11, 2019 $ 0.90 $ 397.8 December 5, 2018 January 14, 2019 December 27, 2018 $ 0.84 $ 370.5 (1) Does not include amounts accrued for distributions payable related to unvested restricted stock units. During the three months ended March 31, 2018 , the Company declared or paid the following cash distributions (per share data reflects actual amounts): Declaration Date Payment Date Record Date Distribution per share Aggregate Payment Amount (1) Common Stock March 8, 2018 April 27, 2018 April 11, 2018 $ 0.75 $ 331.2 December 6, 2017 January 16, 2018 December 28, 2017 $ 0.70 $ 300.2 Series B Preferred Stock January 22, 2018 February 15, 2018 February 1, 2018 $ 13.75 $ 18.9 (1) Does not include amounts accrued for distributions payable related to unvested restricted stock units. The Company accrues distributions on unvested restricted stock units, which are payable upon vesting. As of March 31, 2019 , the amount accrued for distributions payable related to unvested restricted stock units was $8.9 million . During the three months ended March 31, 2019 , the Company paid $6.6 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.

EARNINGS PER COMMON SHARE

EARNINGS PER COMMON SHARE	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
EARNINGS PER COMMON SHARE	EARNINGS PER COMMON SHARE The following table sets forth basic and diluted net income per common share computational data (shares in thousands, except per share data): Three Months Ended March 31, 2019 2018 Net income attributable to American Tower Corporation stockholders $ 397.4 $ 285.2 Dividends on preferred stock — (9.4 ) Net income attributable to American Tower Corporation common stockholders 397.4 275.8 Basic weighted average common shares outstanding 441,351 435,124 Dilutive securities 3,270 3,396 Diluted weighted average common shares outstanding 444,621 438,520 Basic net income attributable to American Tower Corporation common stockholders per common share $ 0.90 $ 0.63 Diluted net income attributable to American Tower Corporation common stockholders per common share $ 0.89 $ 0.63 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, 2019 2018 Restricted stock units 105 118 Stock options — — Preferred stock — 5,904

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Litigation —The Company periodically becomes involved in various claims, lawsuits and proceedings that are incidental to its business. In the opinion of Company management, after consultation with counsel, there are no matters currently pending that would, in the event of an adverse outcome, materially impact the Company’s consolidated financial position, results of operations or liquidity. Verizon Transaction —In March 2015, the Company entered into an agreement with various operating entities of Verizon Communications Inc. (“Verizon”) that currently provides for the lease, sublease or management of approximately 11,250 wireless communications sites commencing March 27, 2015. The average term of the lease or sublease for all sites at the inception of the agreement was approximately 28 years , assuming renewals or extensions of the underlying ground leases for the sites. The Company has the option to purchase the leased sites in tranches, subject to the applicable lease, sublease or management rights upon its scheduled expiration. Each tower is assigned to an annual tranche, ranging from 2034 to 2047, which represents the outside expiration date for the sublease rights to the towers in that tranche. The purchase price for each tranche is a fixed amount stated in the lease for such tranche plus the fair market value of certain alterations made to the related towers. The aggregate purchase option price for the towers leased and subleased is approximately $5.0 billion . Verizon will occupy the sites as a tenant for an initial term of ten years with eight optional successive five -year terms; each such term shall be governed by standard master lease agreement terms established as a part of the transaction. AT&T Transaction —The Company has an agreement with SBC Communications Inc., a predecessor entity to AT&T Inc. (“AT&T”), that currently provides for the lease or sublease of approximately 2,270 towers commencing between December 2000 and August 2004. Substantially all of the towers are part of the securitization transactions completed in March 2013 and March 2018. The average term of the lease or sublease for all sites at the inception of the agreement was approximately 27 years , assuming renewals or extensions of the underlying ground leases for the sites. The Company has the option to purchase the sites subject to the applicable lease or sublease upon its expiration. Each tower is assigned to an annual tranche, ranging from 2013 to 2032, which represents the outside expiration date for the sublease rights to that tower. The purchase price for each site is a fixed amount stated in the lease for that site plus the fair market value of certain alterations made to the related tower by AT&T. As of March 31, 2019 , the Company has purchased an aggregate of 153 of the subleased towers upon expiration of the applicable agreement. The aggregate purchase option price for the remaining towers leased and subleased is $911.4 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, AT&T has the right to continue to lease the reserved space through June 30, 2020 at the then-current monthly fee, which shall escalate in accordance with the standard master lease agreement for the remainder of AT&T’s tenancy. Thereafter, AT&T shall have the right to renew such lease for up to four successive five -year terms. ALLTEL Transaction —In December 2000, the Company entered into an agreement with ALLTEL Communications, LLC, a predecessor entity to Verizon Wireless, to acquire towers through a 15 -year sublease agreement. Pursuant to the agreement, as amended, with Verizon Wireless, the Company acquired rights to approximately 1,800 towers in tranches between April 2001 and March 2002. The Company has the option to purchase each tower at the expiration of the applicable sublease. During the year ended December 31, 2016, the Company exercised the purchase options for 1,523 towers in a single closing and provided notice to the tower owner, Verizon’s assignee, of its intent to exercise the purchase options related to the 243 remaining towers. As of March 31, 2019 , the purchase price per tower was $42,844 payable in cash or, at the tower owner’s option, with 769 shares of the Company’s common stock per tower. The aggregate cash purchase option price for the remaining subleased towers was $10.4 million as of March 31, 2019 . Other Contingencies —The Company is subject to income tax and other taxes in the geographic areas where it operates, and periodically receives notifications of audits, assessments or other actions by taxing authorities. Taxing authorities may issue preliminary notices or assessments while audits are being conducted. In certain jurisdictions, taxing authorities may issue assessments with minimal examination. These notices and assessments do not represent amounts that the Company is obligated to pay and are often not reflective of the actual tax liability for which the Company will ultimately be liable. The Company evaluates the circumstances of each notification or assessment 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. On December 5, 2016, the Company received an income tax assessment of Essar Telecom Infrastructure Private Limited (“ETIPL”) from the India Income Tax Department (the “Tax Department”) for the fiscal year ending 2008 in the amount of 4.75 billion INR ( $69.8 million on the date of assessment) related to capital contributions. The Company challenged the assessment before the Office of Commissioner of Income Tax - Appeals, which ruled in the Company’s favor in January 2018. However, the Tax Department has appealed this ruling at a higher appellate authority. The Company estimates that there is a more likely than not probability that the Company’s position will be sustained upon appeal. Accordingly, no liability has been recorded. Additionally, the assessment was made with respect to transactions that took place in the tax year commencing in 2007, prior to the Company’s acquisition of ETIPL. Under the Company’s definitive acquisition agreement of ETIPL, the seller is obligated to indemnify and defend the Company with respect to any tax-related liability that may arise from activities prior to March 31, 2010.

ACQUISITIONS

ACQUISITIONS	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
ACQUISITIONS	ACQUISITIONS Impact of current year acquisitions —The Company typically acquires communications sites from wireless carriers or other tower operators and subsequently integrates those sites into its existing portfolio of communications sites. The financial results of the Company’s acquisitions have been included in the Company’s consolidated statements of operations for the three months ended March 31, 2019 from the date of the respective acquisition. The date of acquisition, and by extension the point at which the Company begins to recognize the results of an acquisition, may depend on, among other things, the receipt of contractual consents, the commencement and extent of leasing arrangements and the timing of the transfer of title or rights to the assets, which may be accomplished in phases. Sites acquired from communications service providers may never have been operated as a business and may instead have been utilized solely by the seller as a component of its network infrastructure. An acquisition may or may not involve the transfer of business operations or employees. The Company evaluates each of its acquisitions under the accounting guidance framework to determine whether to treat an acquisition as an asset acquisition or a business combination. For those transactions treated as asset acquisitions, the purchase price is allocated to the assets acquired, with no recognition of goodwill. For those acquisitions accounted for as business combinations, the Company recognizes acquisition and merger related expenses in the period in which they are incurred and services are received; for transactions accounted for as asset acquisitions, these costs are capitalized as part of the purchase price. Acquisition and merger related costs may include finder’s fees, advisory, legal, accounting, valuation and other professional or consulting fees and general administrative costs directly related to completing the transaction. Integration costs include incremental and non-recurring costs necessary to convert data, retain employees and otherwise enable the Company to operate acquired businesses or assets efficiently. The Company records acquisition and merger related expenses for business combinations, as well as integration costs for all acquisitions, in Other operating expenses in the consolidated statements of operations. During the three months ended March 31, 2019 and 2018 , the Company recorded acquisition and merger related expenses for business combinations and non-capitalized asset acquisition costs and integration costs as follows: Three Months Ended March 31, 2019 2018 Acquisition and merger related expenses $ 2.0 $ 1.4 Integration costs $ 4.1 $ 0.5 The Company also received $5.7 million related to a pre-acquisition contingency in France during the three months ended March 31, 2019. 2019 Transactions The estimated aggregate impact of the acquisitions completed in 2019 on the Company’s revenues and gross margin for the three months ended March 31, 2019 was approximately $0.4 million and $0.3 million , respectively. The revenues and gross margin amounts also reflect incremental revenues from the addition of new tenants to such sites subsequent to the transaction date. During the three months ended March 31, 2019 , the Company acquired a total of 107 communications sites in the United States, Colombia, Paraguay and Peru, as well as other communications infrastructure assets for an aggregate purchase price of $95.3 million . Tower acquisitions were accounted for as asset acquisitions and the communications infrastructure assets acquisition was accounted for as a business combination. The following table summarizes the allocations of the purchase prices for the fiscal year 2019 acquisitions based upon their estimated fair value at the date of acquisition: Allocation (1) Current assets $ 0.5 Property and equipment 15.5 Intangible assets (2): Tenant-related intangible assets 46.0 Network location intangible assets 6.3 Other intangible assets — Other non-current assets 5.6 Current liabilities (0.7 ) Deferred tax liability — Other non-current liabilities (8.8 ) Net assets acquired 64.4 Goodwill (3) 30.9 Fair value of net assets acquired 95.3 Debt assumed — Purchase price $ 95.3 _______________ (1) Includes 37 sites in Peru held pursuant to long-term finance leases. (2) Tenant-related intangible assets and network location intangible assets are amortized on a straight-line basis over periods of up to 20 years. (3) The Company expects the majority of goodwill to be deductible for tax purposes. 2018 Transactions During the three months ended March 31, 2019 , there were no material post-closing adjustments that impacted the 2018 acquisitions. Pro Forma Consolidated Results (Unaudited) The following table presents the unaudited pro forma financial results as if the 2019 acquisitions had occurred on January 1, 2018 and the 2018 acquisitions had occurred on January 1, 2017. The pro forma results do not include any anticipated cost synergies, costs or other integration impacts. Accordingly, such pro forma amounts are not necessarily indicative of the results that actually would have occurred had the transactions been completed on the date indicated, nor are they indicative of the future operating results of the Company. Three Months Ended March 31, 2019 2018 Pro forma revenues $ 1,814.9 $ 1,844.0 Pro forma net income attributable to American Tower Corporation common stockholders $ 397.9 $ 273.3 Pro forma net income per common share amounts: Basic net income attributable to American Tower Corporation common stockholders $ 0.90 $ 0.63 Diluted net income attributable to American Tower Corporation common stockholders $ 0.89 $ 0.62

BUSINESS SEGMENTS

BUSINESS SEGMENTS	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
BUSINESS SEGMENTS	BUSINESS SEGMENTS The Company’s primary business is leasing space on multitenant communications sites to wireless service providers, radio and television broadcast companies, wireless data providers, government agencies and municipalities and tenants in a number of other industries. This business is referred to as the Company’s property operations, which as of March 31, 2019 , consisted of the following: • U.S.: property operations in the United States; • Asia: property operations in India; • Europe, Middle East and Africa (“EMEA”): property operations in France, Germany, Ghana, Kenya, Nigeria, South Africa and Uganda; and • Latin America: property operations in Argentina, Brazil, Chile, Colombia, Costa Rica, Mexico, Paraguay and Peru. The Company’s services segment offers tower-related services in the United States, including AZP and structural analysis, which primarily support its site leasing business, including the addition of new tenants and equipment on its sites. The services segment is a strategic business unit that offers different services from, and requires different resources, skill sets and marketing strategies than, the property operating segments. The accounting policies applied in compiling segment information below are similar to those described in note 1 to the Company’s consolidated financial statements included in the 2018 Form 10-K and as updated in note 1 above. Among other factors, in evaluating financial performance in each business segment, management uses segment gross margin and segment operating profit. The Company defines segment gross margin as segment revenue less segment operating expenses excluding stock-based compensation expense recorded in costs of operations; Depreciation, amortization and accretion; Selling, general, administrative and development expense; and Other operating expenses. The Company defines segment operating profit as segment gross margin less Selling, general, administrative and development expense attributable to the segment, excluding stock-based compensation expense and corporate expenses. For reporting purposes, for periods through September 30, 2018, the Latin America property segment gross margin and segment operating profit also include Interest income (expense), TV Azteca, net. These measures of segment gross margin and segment operating profit are also before Interest income, Interest expense, Gain (loss) on retirement of long-term obligations, Other income (expense), Net income (loss) attributable to noncontrolling interests and Income tax benefit (provision). The categories of expenses indicated above, such as depreciation, have been excluded from segment operating performance as they are not considered in the review of information or the evaluation of results by management. There are no significant revenues resulting from transactions between the Company’s operating segments. All intercompany transactions are eliminated to reconcile segment results and assets to the consolidated statements of operations and consolidated balance sheets. Summarized financial information concerning the Company’s reportable segments for the three months ended March 31, 2019 and 2018 is shown in the following tables. The “Other” column (i) represents amounts excluded from specific segments, such as business development operations, stock-based compensation expense and corporate expenses included in Selling, general, administrative and development expense; Other operating expenses; Interest income; Interest expense; Gain (loss) on retirement of long-term obligations; and Other income (expense), and (ii) reconciles segment operating profit to Income from continuing operations before income taxes. Property Total Property Services Other Total Three Months Ended March 31, 2019 U.S. Asia EMEA Latin America Segment revenues $ 986.3 $ 288.9 $ 177.5 $ 333.3 $ 1,786.0 $ 27.4 $ 1,813.4 Segment operating expenses (1) 191.3 178.0 59.7 103.4 532.4 10.1 542.5 Segment gross margin 795.0 110.9 117.8 229.9 1,253.6 17.3 1,270.9 Segment selling, general, administrative and development expense (1) 41.7 26.6 18.4 27.7 114.4 3.4 117.8 Segment operating profit 753.3 84.3 99.4 202.2 1,139.2 13.9 1,153.1 Stock-based compensation expense $ 42.5 42.5 Other selling, general, administrative and development expense 38.7 38.7 Depreciation, amortization and accretion 436.9 436.9 Other expense (2) 193.4 193.4 Income from continuing operations before income taxes $ 441.6 Total assets $ 22,160.9 $ 5,427.6 $ 3,637.5 $ 7,306.4 $ 38,532.4 $ 43.8 $ 350.6 $ 38,926.8 _______________ (1) Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $0.9 million and $41.6 million , respectively. (2) Primarily includes interest expense. Property Total Property Services Other Total Three Months Ended March 31, 2018 U.S. Asia EMEA Latin America Segment revenues $ 931.4 $ 273.0 $ 174.2 $ 331.8 $ 1,710.4 $ 31.4 $ 1,741.8 Segment operating expenses (1) 186.3 157.9 59.1 103.4 506.7 12.2 518.9 Interest income, TV Azteca, net — — — 2.7 2.7 — 2.7 Segment gross margin 745.1 115.1 115.1 231.1 1,206.4 19.2 1,225.6 Segment selling, general, administrative and development expense (1) 35.4 44.2 16.8 24.6 121.0 3.5 124.5 Segment operating profit $ 709.7 $ 70.9 $ 98.3 $ 206.5 $ 1,085.4 $ 15.7 1,101.1 Stock-based compensation expense $ 42.7 42.7 Other selling, general, administrative and development expense 38.7 38.7 Depreciation, amortization and accretion 446.3 446.3 Other expense (2) 324.2 $ 324.2 Income from continuing operations before income taxes $ 249.2 Total assets $ 18,894.7 $ 5,796.8 $ 3,343.4 $ 6,084.1 $ 34,119.0 $ 47.0 $ 206.7 $ 34,372.7 _______________ (1) Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $1.0 million and $41.7 million , respectively. (2) Primarily includes interest expense and $147.4 million in impairment charges.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	3 Months Ended
	Mar. 31, 2019
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS Redemption of 5.050% Senior Notes —On April 22, 2019, the Company redeemed all of the 5.050% Notes at a price equal to 103.0050% of the principal amount, plus accrued and unpaid interest up to, but excluding, April 22, 2019, for an aggregate redemption price of $726.0 million , including $5.0 million in accrued and unpaid interest. The Company expects to record a loss on retirement of long-term obligations of approximately $22.1 million , which includes prepayment consideration of $21.0 million and the associated unamortized discount and deferred financing costs. The redemption was funded with borrowings under the 2014 Credit Facility and cash on hand. Upon completion of this redemption, none of the 5.050% Notes remained outstanding. Put Options —In April 2019, Tata Teleservices and Tata Sons delivered notice of exercise of their put options with respect to 100% of their remaining holdings in the Company’s Indian subsidiary, ATC TIPL. The Company expects to complete the redemption of the put shares, subject to regulatory approval, for total consideration of INR 24.8 billion (approximately $358.7 million ) in 2019. After the completion of the redemption, the Company will hold an approximately 92% ownership interest in ATC TIPL.

BASIS OF PRESENTATION AND SIG_2

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	The accompanying consolidated and condensed consolidated financial statements have been prepared by American Tower Corporation (together with its subsidiaries, “ATC” or the “Company”) pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The financial information included herein is unaudited. However, the Company believes that all adjustments, which are of a normal and recurring nature, considered necessary for a fair presentation of its financial position and results of operations for such periods have been included herein. The consolidated and condensed consolidated financial statements and related notes should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 (the “ 2018 Form 10-K”). The results of operations for the three months ended March 31, 2019 are not necessarily indicative of the results that may be expected for the entire year.
Principles of Consolidation and Basis of Presentation	Principles of Consolidation and Basis of Presentation —The accompanying consolidated and condensed consolidated financial statements include the accounts of the Company and those entities in which it has a controlling interest. Investments in entities that the Company does not control are accounted for using the equity 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.
Lease	Lease —The new lease standard requires leases to be accounted for using a right-of-use model, which recognizes that, at the date of commencement, a lessee has a financial obligation to make lease payments to the lessor for the right to use the underlying asset during the lease term. The lessee recognizes a corresponding right-of-use asset related to this right. On January 1, 2019, the Company elected to adopt the new lease standard using the modified retrospective method applied to lease arrangements that were in place on the transition date. Results for reporting periods beginning January 1, 2019 are presented under the new standard, while prior-period amounts are not adjusted and continue to be reported in accordance with accounting under the previously applicable guidance. The Company elected certain available practical expedients which permit the adopter to not reassess certain items upon adoption, including: (i) whether any existing contracts are or contain leases, (ii) the classification of existing leases and (iii) initial direct costs for existing leases. The Company also elected the practical expedient related to easements, which permits carryforward accounting treatment for land easements on existing agreements. The Company recorded a net increase to opening Distributions in excess of earnings in its consolidated balance sheet of $24.7 million as of January 1, 2019 due to the cumulative impact of adopting the new lease standard. This adjustment related to right-of-use asset impairments. The Company also recorded a lease liability of $6.9 billion and a corresponding right-of-use asset of $7.1 billion upon adoption of the new lease standard. Those rights and obligations are primarily related to operating leases for ground space underneath the Company’s communications sites. The right-of-use assets recorded include, among other items, amounts previously classified as prepaid rent, deferred lease acquisition costs, fair value adjustments on acquired leases and long-term deferred rent obligations. Finance leases, which primarily relate to towers, equipment and vehicles, were largely unchanged. There was no significant change to the Company’s consolidated statement of operations resulting from the adoption of this standard. The Company did not elect the practical expedient for short-term leases, which permits an adopter to not apply the lease standard to leases with a remaining maturity of one year or less, and applied the new lease accounting standard to all leases, including short-term leases. In conjunction with the adoption of the new lease accounting guidance, the Company applied the lessor and lessee practical expedient and no longer separates lease and non-lease components within a lease agreement when the timing and pattern of revenue recognition for the components are the same and the combined single lease component is classified as an operating lease. Certain amounts, such as power and fuel and common area maintenance, which were previously reported as non-lease revenue, are now accounted for as lease revenue. Accordingly, the Company has reclassified certain prior-period amounts within its disclosures.
Revenue	Revenue —Most of the Company’s revenue is derived from leasing arrangements and is accounted for as lease revenue unless the timing and pattern of revenue recognition differs from the lease components. Revenue related to distributed antenna system (“DAS”) networks and fiber results from agreements with tenants that are not leases. Non-lease revenue —Non-lease revenue consists primarily of revenue generated from DAS networks, fiber and other property related revenue. DAS networks and fiber arrangements require that the Company provide the tenant the right to use the applicable communications infrastructure. Performance obligations are satisfied over time for the duration of the arrangements. Other property related revenue streams, which include site inspections, are not material on either an individual or consolidated basis. Services revenue —The Company offers tower-related services in the United States. These services include site acquisition, zoning and permitting (“AZP”) and structural analysis. There is a single performance obligation related to AZP, and revenue is recognized over time based on milestones achieved, which are determined based on costs expected to be incurred. Structural analysis services may have more than one performance obligation, contingent upon the number of contracted services. Revenue is recognized at the point in time the services are completed. Revenue —
Accounting Standards Updates	Accounting Standards Updates In January 2017, the FASB issued guidance on accounting for goodwill impairments. The guidance eliminates Step 2 from the goodwill impairment test and requires, among other things, recognition of an impairment loss when the carrying value of a reporting unit exceeds its fair value. The loss recognized is limited to the total amount of goodwill allocated to that reporting unit. The guidance is effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company does not expect the adoption of this guidance to have a material impact on the Company’s financial statements.

BASIS OF PRESENTATION AND SIG_3

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Tables)	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Reconciliation of Cash and Cash Equivalents and Restricted Cash	The reconciliation of cash and cash equivalents and restricted cash reported within the applicable balance sheet that sum to the total of the same such amounts shown in the statement of cash flows is as follows: Three Months Ended March 31, 2019 2018 Cash and cash equivalents $ 1,004.8 $ 1,125.4 Restricted cash 94.9 153.5 Total cash and cash equivalents and restricted cash $ 1,099.7 $ 1,278.9
Summary of Non-lease Revenue Disaggregated by Source and Geography	A summary of non-lease revenue disaggregated by source and geography is as follows: Three Months Ended March 31, 2019 U.S. Asia EMEA Latin America Total Non-lease property revenue $ 58.8 $ 2.4 $ 1.6 $ 35.0 $ 97.8 Services revenue 27.4 — — — 27.4 Total non-lease revenue $ 86.2 $ 2.4 $ 1.6 $ 35.0 $ 125.2 Property lease revenue 927.5 286.5 175.9 298.3 1,688.2 Total revenue $ 1,013.7 $ 288.9 $ 177.5 $ 333.3 $ 1,813.4 Three Months Ended March 31, 2018 (1) U.S. Asia EMEA Latin America Total Non-lease property revenue $ 63.1 $ 1.9 $ 0.6 $ 23.7 $ 89.3 Services revenue 31.4 — — — 31.4 Total non-lease revenue $ 94.5 $ 1.9 $ 0.6 $ 23.7 $ 120.7 Property lease revenue 868.3 271.1 173.6 308.1 1,621.1 Total revenue $ 962.8 $ 273.0 $ 174.2 $ 331.8 $ 1,741.8 _______________ (1) Prior-period amounts adjusted with the adoption of the new lease accounting guidance, as applicable.
Information About Receivables, Contract Assets and Contract Liabilities From Contracts With Tenants	Information about receivables, contract assets and contract liabilities from contracts with tenants is as follows: March 31, 2019 December 31, 2018 (1) Accounts receivable $ 91.9 $ 92.6 Prepaids and other current assets 7.7 7.7 Notes receivable and other non-current assets 21.3 22.2 Unearned revenue (2) 43.2 35.0 Other non-current liabilities (3) 54.1 54.1 _______________ (1) Prior-period amounts adjusted with the adoption of the new lease accounting guidance, as applicable. (2) Excludes $55.9 million and $55.0 million of capital contributions related to DAS networks as of March 31, 2019 and December 31, 2018, respectively. (3) Excludes $302.6 million and $313.6 million of capital contributions related to DAS networks as of March 31, 2019 and December 31, 2018, respectively.

PREPAID AND OTHER CURRENT ASS_2

PREPAID AND OTHER CURRENT ASSETS (Tables)	3 Months Ended
	Mar. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid and other current assets	Prepaid and other current assets consisted of the following: As of March 31, 2019 December 31, 2018 Unbilled receivables $ 131.3 $ 126.1 Prepaid income tax 102.2 125.1 Value added tax and other consumption tax receivables 85.1 86.3 Prepaid assets 54.0 40.5 Prepaid operating ground leases — 165.0 Other miscellaneous current assets 98.6 78.2 Prepaids and other current assets $ 471.2 $ 621.2

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment (including assets held under financing leases) consisted of the following: Estimated Useful Lives (years) (1) As of March 31, 2019 December 31, 2018 Towers Up to 20 $ 12,850.9 $ 12,777.9 Equipment (2) 2 - 20 1,700.7 1,667.3 Buildings and improvements 3 - 32 632.6 628.5 Land and improvements (3) Up to 20 2,318.3 2,285.4 Construction-in-progress 364.8 358.1 Total 17,867.3 17,717.2 Less accumulated depreciation (6,664.7 ) (6,470.1 ) Property and equipment, net $ 11,202.6 $ 11,247.1 _______________ (1) Assets on leased land are depreciated over the shorter of the estimated useful life of the asset or the term of the corresponding ground lease taking into consideration lease renewal options and residual value. (2) Includes fiber and DAS assets. (3) Estimated useful lives apply to improvements only.
Schedule of Finance Lease Assets Included In Property Plant And Equipment	As of December 31, 2018, property and equipment included $4,369.5 million of capital lease assets with related equipment and improvements and $1,016.2 million of accumulated depreciation. Information about finance lease-related balances is as follows: As of Finance leases: Classification March 31, 2019 Property and equipment Towers $ 2,780.9 Accumulated depreciation (1,042.6 ) Property and equipment, net 1,738.3 Property and equipment Buildings and improvements $ 171.1 Accumulated depreciation (60.4 ) Property and equipment, net $ 110.7 Property and equipment Land $ 130.3 Property and equipment Equipment $ 38.1 Accumulated depreciation (9.6 ) Property and equipment, net $ 28.5

LEASES (Tables)

LEASES (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Lessor, Maturities of Minimum Rental Receipts Expected Under Non-cancellable Operating Leases Lease, Payments to be Received, Maturity	Future minimum rental receipts expected under non-cancellable operating lease agreements as of March 31, 2019 were as follows: Fiscal Year Amount (1) Remainder of 2019 $ 3,987.3 2020 5,143.4 2021 4,739.9 2022 3,821.5 2023 3,516.4 Thereafter 13,254.4 Total $ 34,462.9 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods. Future minimum rental receipts expected under non-cancellable operating lease agreements in effect at December 31, 2018 were as follows: Year Ended December 31, Amount (1) 2019 $ 5,251.2 2020 5,062.2 2021 4,676.1 2022 3,754.6 2023 3,457.3 Thereafter 12,641.1 Total $ 34,842.5 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.
Schedule of Information About Other Lease-related Balances	Information about other lease-related balances as of March 31, 2019 is as follows: Operating leases: Right-of-use asset $ 7,080.9 Current portion of lease liabilities $ 498.4 Lease liabilities 6,316.1 Total operating lease liabilities $ 6,814.5 Finance leases: Current portion of lease liabilities $ 6.5 Lease liabilities 21.8 Total finance lease liabilities $ 28.3
Lease Terms And Borrowing Rates	The weighted-average remaining lease terms and incremental borrowing rates as of March 31, 2019 are as follows: Operating leases: Weighted-average remaining lease term (years) 13.0 Weighted-average incremental borrowing rate 6.1 % Finance leases: Weighted-average remaining lease term (years) 9.2 Weighted-average incremental borrowing rate 6.0 %
Components of Operating Lease Cost	The weighted-average remaining lease terms and incremental borrowing rates as of March 31, 2019 are as follows: Operating leases: Weighted-average remaining lease term (years) 13.0 Weighted-average incremental borrowing rate 6.1 % Finance leases: Weighted-average remaining lease term (years) 9.2 Weighted-average incremental borrowing rate 6.0 % The following table sets forth the components of lease cost for the three months ended March 31, 2019 : Operating lease cost $ 255.0 Variable lease costs not included in lease liability (1) 52.3 Finance lease cost: Amortization of right-of-use asset $ 1.8 Interest on lease liabilities 0.4 Total finance lease cost $ 2.2 _______________ (1) Includes property tax paid on behalf of the landlord. Supplemental cash flow information for the three months ended March 31, 2019 is as follows: Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ (234.9 ) Operating cash flows from finance leases $ (0.3 ) Financing cash flows from finance leases $ (1.3 ) Non-cash items: New operating leases $ 62.1 Operating lease modifications and reassessments $ 30.1
Maturity of Operating Lease Liabilities	Maturities of operating and finance lease liabilities as of March 31, 2019 were as follows: Fiscal Year Operating Lease (1) Finance Lease (1) Remainder of 2019 $ 658.0 $ 6.0 2020 870.7 6.8 2021 853.1 3.9 2022 813.3 3.3 2023 773.6 2.0 Thereafter 6,137.5 24.8 Total lease payments 10,106.2 46.8 Less amounts representing interest (3,291.7 ) (18.5 ) Total lease liabilities 6,814.5 28.3 Less current portion of lease liabilities (498.4 ) (6.5 ) Non-current lease liabilities $ 6,316.1 $ 21.8 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.
Maturity of Finance Lease Liabilities	Maturities of operating and finance lease liabilities as of March 31, 2019 were as follows: Fiscal Year Operating Lease (1) Finance Lease (1) Remainder of 2019 $ 658.0 $ 6.0 2020 870.7 6.8 2021 853.1 3.9 2022 813.3 3.3 2023 773.6 2.0 Thereafter 6,137.5 24.8 Total lease payments 10,106.2 46.8 Less amounts representing interest (3,291.7 ) (18.5 ) Total lease liabilities 6,814.5 28.3 Less current portion of lease liabilities (498.4 ) (6.5 ) Non-current lease liabilities $ 6,316.1 $ 21.8 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.
Schedule of Future Minimum Rental Payments for Operating Leases	Future minimum rental payments under non-cancellable operating leases as of December 31, 2018 is as follows: Year Ended December 31, Amount (1) 2019 $ 926.0 2020 904.2 2021 879.8 2022 834.2 2023 792.6 Thereafter 6,173.1 Total $ 10,509.9 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.
Schedule of Future Minimum Lease Payments for Capital Leases	Future minimum rental payments under capital leases in effect as of December 31, 2018 were as follows: Year Ended December 31, Amount (1) 2019 $ 40.7 2020 32.7 2021 27.8 2022 23.7 2023 19.2 Thereafter 117.5 Total 261.6 Less amounts representing interest (82.1 ) Present value of capital lease obligations $ 179.5 _______________ (1) Balances are translated at the applicable period-end exchange rate, which may impact comparability between periods.

GOODWILL AND OTHER INTANGIBLE_2

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in the carrying value of goodwill	The changes in the carrying value of goodwill for each of the Company’s business segments were as follows: Property Services Total U.S. Asia EMEA Latin America Balance as of January 1, 2019 $ 3,382.5 $ 1,045.5 $ 381.3 $ 690.6 $ 2.0 $ 5,501.9 Additions and adjustments (1) 30.1 — — — — 30.1 Effect of foreign currency translation — 9.2 (6.8 ) 3.8 — 6.2 Balance as of March 31, 2019 $ 3,412.6 $ 1,054.7 $ 374.5 $ 694.4 $ 2.0 $ 5,538.2 _______________ (1) Additions consist of $30.9 million resulting from 2019 acquisitions offset by $0.8 million from revisions to prior-year acquisitions due to measurement period adjustments.
Intangible assets subject to amortization	The Company’s other intangible assets subject to amortization consisted of the following: As of March 31, 2019 As of December 31, 2018 Estimated Useful Gross Carrying Value Accumulated Amortization Net Book Value Gross Carrying Value Accumulated Amortization Net Book Value Acquired network location intangibles (1) Up to 20 $ 4,780.2 $ (1,762.3 ) $ 3,017.9 $ 4,780.3 $ (1,704.9 ) $ 3,075.4 Acquired tenant-related intangibles 15-20 11,212.8 (3,278.0 ) 7,934.8 11,156.5 (3,147.2 ) 8,009.3 Acquired licenses and other intangibles 3-20 105.3 (15.2 ) 90.1 104.1 (14.5 ) 89.6 Total other intangible assets $ 16,098.3 $ (5,055.5 ) $ 11,042.8 $ 16,040.9 $ (4,866.6 ) $ 11,174.3 _______________ (1) Acquired network location intangibles are amortized over the shorter of the term of the corresponding ground lease, taking into consideration lease renewal options and residual value, or up to 20 years, as the Company considers these intangibles to be directly related to the tower assets.
Expected future amortization expenses	Based on current exchange rates, the Company expects to record amortization expense as follows over the remaining current year and the five subsequent years: Fiscal Year Amount Remainder of 2019 $ 586.7 2020 763.4 2021 746.9 2022 742.5 2023 738.2 2024 734.9

NOTES RECEIVABLE AND OTHER NO_2

NOTES RECEIVABLE AND OTHER NON-CURRENT ASSETS (Tables)	3 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Schedule Of Notes Receivables And Other Non-current Assets	Notes receivable and other non-current assets consisted of the following: As of March 31, 2019 December 31, 2018 Long-term prepaid ground rent — 607.5 Notes receivable 0.9 1.0 Other miscellaneous assets 278.2 354.1 Notes receivable and other non-current assets $ 279.1 $ 962.6

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	3 Months Ended
	Mar. 31, 2019
Payables and Accruals [Abstract]
Schedule of accrued expenses	Accrued expenses consisted of the following: As of March 31, 2019 December 31, 2018 Accrued property and real estate taxes $ 177.1 $ 169.7 Accrued pass-through costs 80.1 71.2 Amounts payable to tenants 78.2 93.5 Accrued rent 69.6 61.4 Payroll and related withholdings 60.5 90.4 Accrued construction costs 28.1 41.5 Accrued income tax payable 23.3 57.9 Accrued pass-through taxes 9.5 2.2 Other accrued expenses 337.3 360.5 Total accrued expenses $ 863.7 $ 948.3

LONG-TERM OBLIGATIONS (Tables)

LONG-TERM OBLIGATIONS (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Schedule of long-term obligations	Outstanding amounts under the Company’s long-term obligations, reflecting discounts, premiums, debt issuance costs and fair value adjustments due to interest rate swaps consisted of the following: As of March 31, 2019 December 31, 2018 Maturity Date 2018 Term Loan (1) (2) $ — $ 1,499.8 March 29, 2019 2019 Term Loan (1) 1,299.4 — February 13, 2020 2013 Credit Facility (1) 2,340.0 1,875.0 June 28, 2022 2013 Term Loan (1) 995.0 994.8 January 31, 2024 2014 Credit Facility (1) — — January 31, 2024 3.40% senior notes (3) — 1,000.0 February 15, 2019 2.800% senior notes 748.2 747.8 June 1, 2020 5.050% senior notes (4) 698.9 698.7 September 1, 2020 3.300% senior notes 747.5 747.2 February 15, 2021 3.450% senior notes 646.7 646.3 September 15, 2021 5.900% senior notes 498.5 498.4 November 1, 2021 2.250% senior notes 578.9 572.7 January 15, 2022 4.70% senior notes 697.6 697.4 March 15, 2022 3.50% senior notes 993.0 992.6 January 31, 2023 3.000% senior notes 694.1 687.5 June 15, 2023 5.00% senior notes 1,002.2 1,002.1 February 15, 2024 3.375% senior notes 643.5 — May 15, 2024 1.375% senior notes 552.2 564.0 April 4, 2025 4.000% senior notes 742.3 742.1 June 1, 2025 4.400% senior notes 496.2 496.1 February 15, 2026 1.950% senior notes 554.0 566.0 May 22, 2026 3.375% senior notes 986.7 986.3 October 15, 2026 3.125% senior notes 397.4 397.3 January 15, 2027 3.55% senior notes 743.6 743.5 July 15, 2027 3.600% senior notes 692.1 691.9 January 15, 2028 3.950% senior notes 588.9 — March 15, 2029 Total American Tower Corporation debt 18,336.9 17,847.5 Series 2013-2A securities (5) 1,293.8 1,293.4 March 15, 2023 Series 2018-1A securities (5) 493.7 493.5 March 15, 2028 Series 2015-1 notes (6) 349.0 348.8 June 15, 2020 Series 2015-2 notes (7) 520.9 520.8 June 16, 2025 India indebtedness (8) — 240.1 Various India preference shares (9) — 23.9 March 2, 2020 Shareholder loan (10) 53.4 59.9 December 31, 2019 Other subsidiary debt (11) 128.3 152.5 Various Total American Tower subsidiary debt 2,839.1 3,132.9 Finance and capital lease obligations 28.3 179.5 Total 21,204.3 21,159.9 Less current portion of long-term obligations (2,097.2 ) (2,754.8 ) Long-term obligations $ 19,107.1 $ 18,405.1 _______________ (1) Accrues interest at a variable rate. (2) Repaid in full on February 14, 2019 using proceeds from the 2019 Term Loan (as defined below) and cash on hand. (3) Repaid in full on the maturity date in February 2019 with borrowings from the 2013 Credit Facility and the 2014 Credit Facility (each defined below). (4) Repaid in full on April 22, 2019 with borrowings from the 2014 Credit Facility and cash on hand. (5) Maturity date reflects the anticipated repayment date; final legal maturity is March 15, 2048. (6) Maturity date reflects the anticipated repayment date; final legal maturity is June 15, 2045. (7) Maturity date reflects the anticipated repayment date; final legal maturity is June 15, 2050. (8) Denominated in Indian Rupees (“INR”). Included India working capital facilities, remaining debt assumed by the Company in connection with the Viom Acquisition (as defined in note 12) and debt that has been entered into by ATC TIPL. During the three months ended March 31, 2019, the Company repaid all remaining debt assumed in connection with the Viom Acquisition and debt entered into by ATC TIPL. (9) Mandatorily redeemable preference shares (the “Preference Shares”) denominated in INR and classified as debt. The Preference Shares were redeemed on March 2, 2019. (10) Reflects balance owed to the Company’s joint venture partner in Ghana. The Ghana loan is denominated in Ghanaian Cedi (“GHS”). (11) Includes the South African credit facility, which is denominated in South African Rand and amortizes through December 17, 2020, the Colombian credit facility, which is denominated in Colombian Pesos and amortizes through April 24, 2021, the Brazil credit facility, which is denominated in Brazilian Reais and amortizes through January 15, 2022, the Kenya debt, which is denominated in U.S. Dollars (“USD”) and is payable either (i) in future installments subject to the satisfaction of specified conditions or (ii) three years from the note origination date, and U.S. subsidiary debt related to a seller-financed acquisition.
Schedule of line of credit facilities	As of March 31, 2019 , the key terms under the 2013 Credit Facility, the 2014 Credit Facility, the Company’s unsecured term loan entered into in October 2013, as amended (the “2013 Term Loan”) and the 2019 Term Loan were as follows: Outstanding Principal Balance (in millions) Undrawn letters of credit (in millions) Maturity Date Current margin over LIBOR (1) Current commitment fee (2) 2013 Credit Facility $ 2,340.0 $ 3.8 June 28, 2022 (3) 1.125 % 0.125 % 2014 Credit Facility $ — $ 6.2 January 31, 2024 (3) 1.125 % 0.125 % 2013 Term Loan $ 1,000.0 N/A January 31, 2024 1.125 % N/A 2019 Term Loan $ 1,300.0 N/A February 13, 2020 0.800 % N/A _______________ (1) LIBOR means the London Interbank Offered Rate. (2) Fee on undrawn portion of each credit facility. (3) Subject to two optional renewal periods.

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of fair value of assets and liabilities	The fair values of the Company’s financial assets and liabilities that are required to be measured on a recurring basis at fair value were as follows: March 31, 2019 December 31, 2018 Fair Value Measurements Using Fair Value Measurements Using Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Assets: Short-term investments (1) — $ 18.4 — — — — Embedded derivative in lease agreement — — $ 11.3 — — $ 11.5 Liabilities: Interest rate swap agreements — $ 21.8 — — $ 33.8 — Acquisition-related contingent consideration — — $ 0.8 — — $ 0.9 Fair value of debt related to interest rate swap agreements (2) $ (19.0 ) — — $ (31.3 ) — — Redeemable noncontrolling interests — — $ 589.0 — — $ 1,004.8 _______________ (1) Consists of mutual funds with a portfolio duration of approximately 90 days. (2) Included in the carrying values of the corresponding debt obligations.

INCOME TAXES (Tables)

INCOME TAXES (Tables)	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of penalties and income tax-related interest expense	The Company recorded the following penalties and income tax-related interest expense during the three months ended March 31, 2019 and 2018: Three Months Ended March 31, 2019 2018 Penalties and income tax-related interest expense $ 1.1 $ 1.0

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of stock-based compensation expenses	During the three months ended March 31, 2019 and 2018 , the Company recorded and capitalized the following stock-based compensation expense: Three Months Ended March 31, 2019 2018 Stock-based compensation expense Property $ 0.6 $ 0.7 Stock-based compensation expense Services 0.3 0.3 Stock-based compensation expense SG&A 41.6 41.7 Total stock-based compensation expense $ 42.5 $ 42.7 Stock-based compensation expense capitalized as property and equipment $ 0.5 $ 0.5
Summary of the company's option activity	The Company’s option activity for the three months ended March 31, 2019 was as follows (shares disclosed in full amounts): Number of Options Outstanding as of January 1, 2019 4,257,470 Granted — Exercised (314,847 ) Forfeited — Expired — Outstanding as of March 31, 2019 3,942,623
Summary of the company's restricted stock unit activity	The Company’s RSU and PSU activity for the three months ended March 31, 2019 was as follows (shares disclosed in full amounts): RSUs PSUs Outstanding as of January 1, 2019 (1) 1,649,973 624,511 Granted (2) 539,905 114,823 Vested and Released (3) (607,845 ) (292,180 ) Forfeited (13,599 ) — Outstanding as of March 31, 2019 1,568,434 447,154 Vested and deferred as of March 31, 2019 (4) 32,596 46,500 _______________ (1) PSUs consist of the target number of shares issuable at the end of the three -year performance period for the 2018 PSUs and 2017 PSUs, or 131,311 and 154,520 shares, respectively, and the shares issuable at the end of the three -year performance period for the PSUs granted in 2016 (“2016 PSUs”) based on achievement against the performance metrics for the three-year performance period, or 338,680 shares. (2) PSUs consist of the target number of shares issuable at the end of the three -year performance period for the 2019 PSUs, or 114,823 shares. (3) PSUs consist of shares vested pursuant to the 2016 PSUs. There are no additional shares to be earned related to the 2016 PSUs. (4) Vested and deferred RSUs and PSUs are related to deferred compensation for certain former employees.

REDEEMABLE NONCONTROLLING INT_2

REDEEMABLE NONCONTROLLING INTERESTS (Tables)	3 Months Ended
	Mar. 31, 2019
Noncontrolling Interest [Abstract]
Changes in Redeemable noncontrolling interest	The changes in Redeemable noncontrolling interests for the three months ended March 31, 2019 and 2018 were as follows: Three Months Ended March 31, 2019 2018 Balance as of January 1, $ 1,004.8 $ 1,126.2 Net loss attributable to noncontrolling interests (3.7 ) (28.1 ) Adjustment to noncontrolling interest redemption value 3.7 17.5 Adjustment to noncontrolling interest due to merger — (28.1 ) Purchase of noncontrolling interest (425.7 ) — Foreign currency translation adjustment attributable to noncontrolling interests 9.9 (22.3 ) Balance as of March 31, $ 589.0 $ 1,065.2

EQUITY (Tables)

EQUITY (Tables)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Schedule of declared or paid cash distributions	During the three months ended March 31, 2019 , the Company declared or paid the following cash distributions (per share data reflects actual amounts): Declaration Date Payment Date Record Date Distribution per share Aggregate Payment Amount (1) Common Stock March 7, 2019 April 26, 2019 April 11, 2019 $ 0.90 $ 397.8 December 5, 2018 January 14, 2019 December 27, 2018 $ 0.84 $ 370.5 (1) Does not include amounts accrued for distributions payable related to unvested restricted stock units. During the three months ended March 31, 2018 , the Company declared or paid the following cash distributions (per share data reflects actual amounts): Declaration Date Payment Date Record Date Distribution per share Aggregate Payment Amount (1) Common Stock March 8, 2018 April 27, 2018 April 11, 2018 $ 0.75 $ 331.2 December 6, 2017 January 16, 2018 December 28, 2017 $ 0.70 $ 300.2 Series B Preferred Stock January 22, 2018 February 15, 2018 February 1, 2018 $ 13.75 $ 18.9 (1) Does not include amounts accrued for distributions payable related to unvested restricted stock units.

EARNINGS PER COMMON SHARE (Tabl

EARNINGS PER COMMON SHARE (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Schedule of earnings per basic and diluted by common class	The following table sets forth basic and diluted net income per common share computational data (shares in thousands, except per share data): Three Months Ended March 31, 2019 2018 Net income attributable to American Tower Corporation stockholders $ 397.4 $ 285.2 Dividends on preferred stock — (9.4 ) Net income attributable to American Tower Corporation common stockholders 397.4 275.8 Basic weighted average common shares outstanding 441,351 435,124 Dilutive securities 3,270 3,396 Diluted weighted average common shares outstanding 444,621 438,520 Basic net income attributable to American Tower Corporation common stockholders per common share $ 0.90 $ 0.63 Diluted net income attributable to American Tower Corporation common stockholders per common share $ 0.89 $ 0.63
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, 2019 2018 Restricted stock units 105 118 Stock options — — Preferred stock — 5,904

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Schedule of acquisition and merger related costs	During the three months ended March 31, 2019 and 2018 , the Company recorded acquisition and merger related expenses for business combinations and non-capitalized asset acquisition costs and integration costs as follows: Three Months Ended March 31, 2019 2018 Acquisition and merger related expenses $ 2.0 $ 1.4 Integration costs $ 4.1 $ 0.5
Schedule of recognized identified assets acquired and liabilities assumed	The following table summarizes the allocations of the purchase prices for the fiscal year 2019 acquisitions based upon their estimated fair value at the date of acquisition: Allocation (1) Current assets $ 0.5 Property and equipment 15.5 Intangible assets (2): Tenant-related intangible assets 46.0 Network location intangible assets 6.3 Other intangible assets — Other non-current assets 5.6 Current liabilities (0.7 ) Deferred tax liability — Other non-current liabilities (8.8 ) Net assets acquired 64.4 Goodwill (3) 30.9 Fair value of net assets acquired 95.3 Debt assumed — Purchase price $ 95.3 _______________ (1) Includes 37 sites in Peru held pursuant to long-term finance leases. (2) Tenant-related intangible assets and network location intangible assets are amortized on a straight-line basis over periods of up to 20 years. (3) The Company expects the majority of goodwill to be deductible for tax purposes.
Schedule of pro forma information	The following table presents the unaudited pro forma financial results as if the 2019 acquisitions had occurred on January 1, 2018 and the 2018 acquisitions had occurred on January 1, 2017. The pro forma results do not include any anticipated cost synergies, costs or other integration impacts. Accordingly, such pro forma amounts are not necessarily indicative of the results that actually would have occurred had the transactions been completed on the date indicated, nor are they indicative of the future operating results of the Company. Three Months Ended March 31, 2019 2018 Pro forma revenues $ 1,814.9 $ 1,844.0 Pro forma net income attributable to American Tower Corporation common stockholders $ 397.9 $ 273.3 Pro forma net income per common share amounts: Basic net income attributable to American Tower Corporation common stockholders $ 0.90 $ 0.63 Diluted net income attributable to American Tower Corporation common stockholders $ 0.89 $ 0.62

BUSINESS SEGMENTS (Tables)

BUSINESS SEGMENTS (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Summarized financial information concerning the company's reportable segments	Summarized financial information concerning the Company’s reportable segments for the three months ended March 31, 2019 and 2018 is shown in the following tables. The “Other” column (i) represents amounts excluded from specific segments, such as business development operations, stock-based compensation expense and corporate expenses included in Selling, general, administrative and development expense; Other operating expenses; Interest income; Interest expense; Gain (loss) on retirement of long-term obligations; and Other income (expense), and (ii) reconciles segment operating profit to Income from continuing operations before income taxes. Property Total Property Services Other Total Three Months Ended March 31, 2019 U.S. Asia EMEA Latin America Segment revenues $ 986.3 $ 288.9 $ 177.5 $ 333.3 $ 1,786.0 $ 27.4 $ 1,813.4 Segment operating expenses (1) 191.3 178.0 59.7 103.4 532.4 10.1 542.5 Segment gross margin 795.0 110.9 117.8 229.9 1,253.6 17.3 1,270.9 Segment selling, general, administrative and development expense (1) 41.7 26.6 18.4 27.7 114.4 3.4 117.8 Segment operating profit 753.3 84.3 99.4 202.2 1,139.2 13.9 1,153.1 Stock-based compensation expense $ 42.5 42.5 Other selling, general, administrative and development expense 38.7 38.7 Depreciation, amortization and accretion 436.9 436.9 Other expense (2) 193.4 193.4 Income from continuing operations before income taxes $ 441.6 Total assets $ 22,160.9 $ 5,427.6 $ 3,637.5 $ 7,306.4 $ 38,532.4 $ 43.8 $ 350.6 $ 38,926.8 _______________ (1) Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $0.9 million and $41.6 million , respectively. (2) Primarily includes interest expense. Property Total Property Services Other Total Three Months Ended March 31, 2018 U.S. Asia EMEA Latin America Segment revenues $ 931.4 $ 273.0 $ 174.2 $ 331.8 $ 1,710.4 $ 31.4 $ 1,741.8 Segment operating expenses (1) 186.3 157.9 59.1 103.4 506.7 12.2 518.9 Interest income, TV Azteca, net — — — 2.7 2.7 — 2.7 Segment gross margin 745.1 115.1 115.1 231.1 1,206.4 19.2 1,225.6 Segment selling, general, administrative and development expense (1) 35.4 44.2 16.8 24.6 121.0 3.5 124.5 Segment operating profit $ 709.7 $ 70.9 $ 98.3 $ 206.5 $ 1,085.4 $ 15.7 1,101.1 Stock-based compensation expense $ 42.7 42.7 Other selling, general, administrative and development expense 38.7 38.7 Depreciation, amortization and accretion 446.3 446.3 Other expense (2) 324.2 $ 324.2 Income from continuing operations before income taxes $ 249.2 Total assets $ 18,894.7 $ 5,796.8 $ 3,343.4 $ 6,084.1 $ 34,119.0 $ 47.0 $ 206.7 $ 34,372.7 _______________ (1) Segment operating expenses and segment selling, general, administrative and development expenses exclude stock-based compensation expense of $1.0 million and $41.7 million , respectively. (2) Primarily includes interest expense and $147.4 million in impairment charges.

BASIS OF PRESENTATION AND SIG_4

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Details)	3 Months Ended
	Mar. 31, 2019joint_venture
Concentration Risk [Line Items]
Number of joint ventures the Company has a controlling interest in (in joint ventures)	2
Ghana
Concentration Risk [Line Items]
Number of joint ventures the Company has a controlling interest in (in joint ventures)	1
Uganda
Concentration Risk [Line Items]
Number of joint ventures the Company has a controlling interest in (in joint ventures)	1
ATC Europe
Concentration Risk [Line Items]
Ownership interest (as a percent)	51.00%
Noncontrolling interest, ownership percentage by noncontrolling owners (as a percent)	49.00%
ATC, TIPL
Concentration Risk [Line Items]
Ownership interest (as a percent)	79.00%
Corporate Joint Venture | Ghana
Concentration Risk [Line Items]
Ownership interest (as a percent)	51.00%
Noncontrolling interest, ownership percentage by noncontrolling owners (as a percent)	49.00%
Corporate Joint Venture | SOUTH AFRICA
Concentration Risk [Line Items]
Ownership interest (as a percent)	81.00%
Noncontrolling interest, ownership percentage by noncontrolling owners (as a percent)	19.00%

BASIS OF PRESENTATION AND SIG_5

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 1,004.8	$ 1,208.7	$ 1,125.4
Restricted cash	94.9	96.2	153.5
Total cash and cash equivalents and restricted cash	$ 1,099.7	$ 1,304.9	$ 1,278.9	$ 954.9

BASIS OF PRESENTATION AND SIG_6

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Leases (Details) - USD ($) $ in Millions	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Distributions in excess of earnings	$ (1,226.4)		$ (1,199.5)
Lease liability	6,814.5
Right-of-use asset	$ 7,080.9		$ 0
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Distributions in excess of earnings		$ 24.7
Lease liability		6,900
Right-of-use asset		$ 7,100

BASIS OF PRESENTATION AND SIG_7

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Summary of Non-lease Revenue Disaggregated by Source and Geography (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 1,813.4	$ 1,741.8
Non-lease property revenue
Disaggregation of Revenue [Line Items]
Total revenue	97.8	89.3
Services revenue
Disaggregation of Revenue [Line Items]
Total revenue	27.4	31.4
Total non-lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	125.2	120.7
Property lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	1,688.2	1,621.1
U.S.
Disaggregation of Revenue [Line Items]
Total revenue	1,013.7	962.8
U.S. | Non-lease property revenue
Disaggregation of Revenue [Line Items]
Total revenue	58.8	63.1
U.S. | Services revenue
Disaggregation of Revenue [Line Items]
Total revenue	27.4	31.4
U.S. | Total non-lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	86.2	94.5
U.S. | Property lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	927.5	868.3
Asia
Disaggregation of Revenue [Line Items]
Total revenue	288.9	273
Asia | Non-lease property revenue
Disaggregation of Revenue [Line Items]
Total revenue	2.4	1.9
Asia | Services revenue
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Asia | Total non-lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	2.4	1.9
Asia | Property lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	286.5	271.1
EMEA
Disaggregation of Revenue [Line Items]
Total revenue	177.5	174.2
EMEA | Non-lease property revenue
Disaggregation of Revenue [Line Items]
Total revenue	1.6	0.6
EMEA | Services revenue
Disaggregation of Revenue [Line Items]
Total revenue	0	0
EMEA | Total non-lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	1.6	0.6
EMEA | Property lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	175.9	173.6
Latin America
Disaggregation of Revenue [Line Items]
Total revenue	333.3	331.8
Latin America | Non-lease property revenue
Disaggregation of Revenue [Line Items]
Total revenue	35	23.7
Latin America | Services revenue
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Latin America | Total non-lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	35	23.7
Latin America | Property lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	$ 298.3	$ 308.1

BASIS OF PRESENTATION AND SIG_8

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Receivables, Contract Assets and Contract Liabilities from Contracts with Tenants (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Schedule of Contract Assets And Liabilities From Contracts With Customers [Line Items]
Prepaids and other current assets	$ 471.2		$ 621.2
Notes receivable and other non-current assets	279.1		962.6
Other non-current liabilities	864.4		1,265.1
Revenue recognized	14.1	$ 10.4
Non-lease revenue
Schedule of Contract Assets And Liabilities From Contracts With Customers [Line Items]
Accounts receivable	91.9		92.6
Prepaids and other current assets	7.7		7.7
Notes receivable and other non-current assets	21.3		22.2
Unearned revenue	43.2		35
Other non-current liabilities	54.1		54.1
Non-lease property revenue | DAS
Schedule of Contract Assets And Liabilities From Contracts With Customers [Line Items]
Unearned revenue	55.9		55
Other non-current liabilities	302.6		$ 313.6
Revenue recognized	14.5	13.8
Other non-current liabilities
Schedule of Contract Assets And Liabilities From Contracts With Customers [Line Items]
Revenue recognized	0.1	0.1
Prepaids and other current assets
Schedule of Contract Assets And Liabilities From Contracts With Customers [Line Items]
Decrease in unbilled receivables due to revenue recognized (less than)	0.1	0.1
Change in contract assets attributable to revenue recognized	$ (0.8)	$ (0.1)

PREPAID AND OTHER CURRENT ASS_3

PREPAID AND OTHER CURRENT ASSETS (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Unbilled receivables	$ 131.3	$ 126.1
Prepaid income tax	102.2	125.1
Value added tax and other consumption tax receivables	85.1	86.3
Prepaid assets	54	40.5
Prepaid operating ground leases	0	165
Other miscellaneous current assets	98.6	78.2
Prepaids and other current assets	$ 471.2	$ 621.2

PROPERTY AND EQUIPMENT (Details

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Towers	$ 12,850.9		$ 12,777.9
Equipment	1,700.7		1,667.3
Buildings and improvements	632.6		628.5
Land and improvements	2,318.3		2,285.4
Construction-in-progress	364.8		358.1
Total	17,867.3		17,717.2
Less accumulated depreciation	(6,664.7)		(6,470.1)
Property and equipment, net	11,202.6		11,247.1
Depreciation	223.7	$ 222.5
Capital leased assets			4,369.5
Capital lease accumulated depreciation			$ 1,016.2
Amortization of right-of-use asset	$ 1.8
Towers | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)	20 years
Equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)	2 years
Equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)	20 years
Building Improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)	3 years
Building Improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)	32 years
Other | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)	20 years
Finance Lease Assets
Property, Plant and Equipment [Line Items]
Amortization of right-of-use asset	$ 42.4

PROPERTY AND EQUIPMENT - Financ

PROPERTY AND EQUIPMENT - Finance Leases Included in Property Plan and Equipment (Details) $ in Millions	Mar. 31, 2019USD ($)
Property, Plant and Equipment [Line Items]
Land easements, not depreciable	$ 1,458.1
Towers
Property, Plant and Equipment [Line Items]
Property and equipment	2,780.9
Accumulated depreciation	(1,042.6)
Property and equipment, net	1,738.3
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property and equipment	171.1
Accumulated depreciation	(60.4)
Property and equipment, net	110.7
Land
Property, Plant and Equipment [Line Items]
Property and equipment	130.3
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment	38.1
Accumulated depreciation	(9.6)
Property and equipment, net	$ 28.5

LEASES - Narrative (Details)

LEASES - Narrative (Details)	3 Months Ended
	Mar. 31, 2019
Minimum
Lessor, Lease, Description [Line Items]
Lessor, terms of contract	5 years
Maximum
Lessor, Lease, Description [Line Items]
Lessor, terms of contract	10 years
Maximum | Communication Sites
Lessor, Lease, Description [Line Items]
Estimated economic life	20 years

LEASES - Maturities of Minimum

LEASES - Maturities of Minimum Rental Receipts Expected Under Non-cancellable Operating Leases (Details) $ in Millions	Mar. 31, 2019USD ($)
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
Remainder of 2019	$ 3,987.3
2020	5,143.4
2021	4,739.9
2022	3,821.5
2023	3,516.4
Thereafter	13,254.4
Total	$ 34,462.9

LEASES - Schedule of Future Min

LEASES - Schedule of Future Minimum Rental Receipts Expected Before Topic 842 (Details) $ in Millions	Dec. 31, 2018USD ($)
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
2019	$ 5,251.2
2020	5,062.2
2021	4,676.1
2022	3,754.6
2023	3,457.3
Thereafter	12,641.1
Total	$ 34,842.5

LEASES - Schedule of Informatio

LEASES - Schedule of Information About Other Lease Related Balances (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Operating leases:
Right-of-use asset	$ 7,080.9	$ 0
Current portion of lease liabilities	498.4	0
Lease liabilities	6,316.1	$ 0
Total operating lease liabilities	6,814.5
Finance leases:
Current portion of lease liabilities	6.5
Lease liabilities	21.8
Total finance lease liabilities	$ 28.3

LEASES - Schedule of Weighted A

LEASES - Schedule of Weighted Average Lease Terms and Discount Rates by Segment (Details)	Mar. 31, 2019
Operating leases:
Weighted-average remaining lease term (years)	13 years
Weighted-average incremental borrowing rate	6.10%
Finance leases:
Weighted-average remaining lease term (years)	9 years 2 months 14 days
Weighted-average incremental borrowing rate	6.00%

LEASES - Lease Costs (Details)

LEASES - Lease Costs (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Operating lease cost	$ 255
Variable lease payments not included in lease liability	52.3
Finance lease cost:
Amortization of right-of-use asset	1.8
Interest on lease liabilities	0.4
Total finance lease cost	$ 2.2

LEASES - Supplemental Cash Flow

LEASES - Supplemental Cash Flow Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ (234.9)
Operating cash flows from finance leases	(0.3)
Financing cash flows from finance leases	(1.3)
Non-cash items:
New operating leases	62.1
Operating lease modifications and reassessments	$ 30.1

LEASES - Maturities of Operatin

LEASES - Maturities of Operating and Finance Lease Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Operating Lease
Remainder of 2019	$ 658
2020	870.7
2021	853.1
2022	813.3
2023	773.6
Thereafter	6,137.5
Total lease payments	10,106.2
Less amounts representing interest	(3,291.7)
Total operating lease liabilities	6,814.5
Less current portion of lease liabilities	(498.4)	$ 0
Non-current lease liabilities	6,316.1	0
Finance Lease
Remainder of 2019	6
2020	6.8
2021	3.9
2022	3.3
2023	2
Thereafter	24.8
Total lease payments	46.8
Less amounts representing interest	(18.5)
Total finance lease liabilities	28.3
Less current portion of lease liabilities	(6.5)
Non-current lease liabilities	21.8
Operating Leases Before Adoption of 842 [Abstract]
2019	926
2020	904.2
2021	879.8
2022	834.2
2023	792.6
Thereafter	6,173.1
Total	$ 10,509.9
Capital Leases Before Adoption of 842
2019		40.7
2020		32.7
2021		27.8
2022		23.7
2023		19.2
Thereafter		117.5
Total		261.6
Less amounts representing interest		(82.1)
Present value of capital lease obligations		179.5
Land Easements
Capital Leases Before Adoption of 842
Total		220.3
Less amounts representing interest		$ (69.3)

GOODWILL AND OTHER INTANGIBLE_3

GOODWILL AND OTHER INTANGIBLE ASSETS - CHANGES IN THE CARRYING VALUE OF GOODWILL (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 5,501.9
Additions and adjustments	30.1
Effect of foreign currency translation	6.2
Goodwill, ending balance	5,538.2
Other Acquisitions 2019
Goodwill [Roll Forward]
Goodwill, ending balance	30.9
Property | U.S.
Goodwill [Roll Forward]
Goodwill, beginning balance	3,382.5
Additions and adjustments	30.1
Effect of foreign currency translation	0
Goodwill, ending balance	3,412.6
Goodwill, purchase accounting adjustments	0.8
Property | U.S. | Other Acquisitions 2019
Goodwill [Roll Forward]
Additions and adjustments	30.9
Property | Asia
Goodwill [Roll Forward]
Goodwill, beginning balance	1,045.5
Additions and adjustments	0
Effect of foreign currency translation	9.2
Goodwill, ending balance	1,054.7
Property | EMEA
Goodwill [Roll Forward]
Goodwill, beginning balance	381.3
Additions and adjustments	0
Effect of foreign currency translation	(6.8)
Goodwill, ending balance	374.5
Property | Latin America
Goodwill [Roll Forward]
Goodwill, beginning balance	690.6
Additions and adjustments	0
Effect of foreign currency translation	3.8
Goodwill, ending balance	694.4
Services
Goodwill [Roll Forward]
Goodwill, beginning balance	2
Additions and adjustments	0
Effect of foreign currency translation	0
Goodwill, ending balance	$ 2

GOODWILL AND OTHER INTANGIBLE_4

GOODWILL AND OTHER INTANGIBLE ASSETS - INTANGIBLE ASSETS SUBJECT TO AMORTIZATION (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 16,098.3	$ 16,040.9
Accumulated Amortization	(5,055.5)	(4,866.6)
Net Book Value	11,042.8	11,174.3
Acquired network location intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	4,780.2	4,780.3
Accumulated Amortization	(1,762.3)	(1,704.9)
Net Book Value	$ 3,017.9	3,075.4
Acquired network location intangibles | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives	0 years
Acquired network location intangibles | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives	20 years
Acquired tenant-related intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 11,212.8	11,156.5
Accumulated Amortization	(3,278)	(3,147.2)
Net Book Value	$ 7,934.8	8,009.3
Acquired tenant-related intangibles | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives	15 years
Acquired tenant-related intangibles | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives	20 years
Acquired licenses and other intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 105.3	104.1
Accumulated Amortization	(15.2)	(14.5)
Net Book Value	$ 90.1	$ 89.6
Acquired licenses and other intangibles | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives	3 years
Acquired licenses and other intangibles | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives	20 years

GOODWILL AND OTHER INTANGIBLE_5

GOODWILL AND OTHER INTANGIBLE ASSETS - NARRATIVE (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 192.7	$ 202.4
Weighted Average
Finite-Lived Intangible Assets [Line Items]
Remaining amortization period	14 years

GOODWILL AND OTHER INTANGIBLE_6

GOODWILL AND OTHER INTANGIBLE ASSETS - EXPECTED FUTURE AMORTIZATION EXPENSE (Details) $ in Millions	Mar. 31, 2019USD ($)
Fiscal Year
Remainder of 2019	$ 586.7
2020	763.4
2021	746.9
2022	742.5
2023	738.2
2024	$ 734.9

NOTES RECEIVABLE AND OTHER NO_3

NOTES RECEIVABLE AND OTHER NON-CURRENT ASSETS (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Receivables [Abstract]
Long-term prepaid ground rent	$ 0	$ 607.5
Notes receivable	0.9	1
Other miscellaneous assets	278.2	354.1
Notes receivable and other non-current assets	$ 279.1	$ 962.6

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued property and real estate taxes	$ 177.1	$ 169.7
Accrued pass-through costs	80.1	71.2
Amounts payable to tenants	78.2	93.5
Accrued rent	69.6	61.4
Payroll and related withholdings	60.5	90.4
Accrued construction costs	28.1	41.5
Accrued income tax payable	23.3	57.9
Accrued pass-through taxes	9.5	2.2
Other accrued expenses	337.3	360.5
Total accrued expenses	$ 863.7	$ 948.3

LONG-TERM OBLIGATIONS - SCHEDUL

LONG-TERM OBLIGATIONS - SCHEDULE OF LONG-TERM OBLIGATIONS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 15, 2019	Feb. 15, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Finance and capital lease obligations				$ 28.3	$ 179.5
Total	$ 21,204.3			21,159.9
Less current portion long-term obligations	(2,097.2)			(2,754.8)
Long-term obligations	19,107.1			18,405.1
American Tower Corporation
Debt Instrument [Line Items]
Long-term debt	18,336.9			17,847.5
American Tower subsidiary
Debt Instrument [Line Items]
Long-term debt	2,839.1			3,132.9
2018 Term Loan | Unsecured debt
Debt Instrument [Line Items]
Long-term debt	0			1,499.8
2019 Term Loan | Unsecured debt
Debt Instrument [Line Items]
Long-term debt	1,299.4			0
2013 Credit Facility | Credit Facility
Debt Instrument [Line Items]
Line of credit	2,340			1,875
2013 Term Loan | Unsecured debt
Debt Instrument [Line Items]
Long-term debt	995			994.8
2014 Credit Facility | Credit Facility
Debt Instrument [Line Items]
Line of credit	0			0
3.40% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 0			1,000
Long-term debt, stated interest rate (as a percent)	3.40%		3.40%
2.800% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 748.2			747.8
Long-term debt, stated interest rate (as a percent)	2.80%
5.050% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 698.9			698.7
Long-term debt, stated interest rate (as a percent)	5.05%
3.300% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 747.5			747.2
Long-term debt, stated interest rate (as a percent)	3.30%
3.450% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 646.7			646.3
Long-term debt, stated interest rate (as a percent)	3.45%
5.900% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 498.5			498.4
Long-term debt, stated interest rate (as a percent)	5.90%
2.250% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 578.9			572.7
Long-term debt, stated interest rate (as a percent)	2.25%
4.70% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 697.6			697.4
Long-term debt, stated interest rate (as a percent)	4.70%
3.50% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 993			992.6
Long-term debt, stated interest rate (as a percent)	3.50%
3.000% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 694.1			687.5
Long-term debt, stated interest rate (as a percent)	3.00%
5.00% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 1,002.2			1,002.1
Long-term debt, stated interest rate (as a percent)	5.00%
3.375% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 643.5			0
Long-term debt, stated interest rate (as a percent)	3.375%
1.375% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 552.2			564
Long-term debt, stated interest rate (as a percent)	1.375%
4.000% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 742.3			742.1
Long-term debt, stated interest rate (as a percent)	4.00%
4.400% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 496.2			496.1
Long-term debt, stated interest rate (as a percent)	4.40%
1.950% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 554			566
Long-term debt, stated interest rate (as a percent)	1.95%
3.375% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 986.7			986.3
Long-term debt, stated interest rate (as a percent)	3.375%	3.375%
3.125% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 397.4			397.3
Long-term debt, stated interest rate (as a percent)	3.125%
3.55% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 743.6			743.5
Long-term debt, stated interest rate (as a percent)	3.55%
3.600% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 692.1			691.9
Long-term debt, stated interest rate (as a percent)	3.60%
3.950% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt	$ 588.9			0
Long-term debt, stated interest rate (as a percent)	3.95%	3.95%
Series 2013-2A securities | Secured debt | Series 2013-2A securities
Debt Instrument [Line Items]
Long-term debt	$ 1,293.8			1,293.4
Series 2018-1A securities | Secured debt | Series 2018-1A securities
Debt Instrument [Line Items]
Long-term debt	493.7			493.5
Series 2015-1 notes | Secured debt
Debt Instrument [Line Items]
Long-term debt	349			348.8
Series 2015-2 notes | Secured debt
Debt Instrument [Line Items]
Long-term debt	520.9			520.8
India indebtedness | Unsecured debt
Debt Instrument [Line Items]
Long-term debt	0			240.1
India preference shares | Mandatorily redeemable preferred stock
Debt Instrument [Line Items]
Long-term debt	0			23.9
Shareholder loans | Unsecured debt
Debt Instrument [Line Items]
Long-term debt	53.4			59.9
Other subsidiary debt | Unsecured debt
Debt Instrument [Line Items]
Long-term debt	$ 128.3			$ 152.5
Debt repayment period	3 years

LONG-TERM OBLIGATIONS - NARRATI

LONG-TERM OBLIGATIONS - NARRATIVE (Details) GH₵ in Millions, $ in Millions	Mar. 15, 2019EUR (€)	Feb. 15, 2019USD ($)	May 22, 2018	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)	Mar. 31, 2019GHS (GH₵)	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Current portion of long-term obligations				$ 2,097.2			$ 2,754.8
Proceeds from term loan				1,300	$ 1,500
Borrowings under credit facilities				1,700	$ 1,748.3
2013 Credit Facility | Credit Facility
Debt Instrument [Line Items]
Borrowings under credit facilities				995
Repayment of indebtedness under credit facility				530
2014 Credit Facility | Credit Facility
Debt Instrument [Line Items]
Borrowings under credit facilities				705
Repayment of indebtedness under credit facility				705
Unsecured debt | 2019 Term Loan
Debt Instrument [Line Items]
Current portion of long-term obligations				1,300
Unsecured debt | Shareholder loans
Debt Instrument [Line Items]
Current portion of long-term obligations				$ 53.4		GH₵ 294.4
Senior notes
Debt Instrument [Line Items]
Redemption price (as a percent)			100.00%
Redemption price, change in control and corresponding ratings decline (as percent)	101.00%
Maximum adjusted EBITDA				3.5		3.5
Senior notes | 5.050% senior notes
Debt Instrument [Line Items]
Current portion of long-term obligations				$ 698.9
Long-term debt, stated interest rate (as a percent)				5.05%		5.05%
Senior notes | 3.40% senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)		3.40%		3.40%		3.40%
Repayments of senior debt		$ 1,000
Senior notes | 3.375% senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.375%			3.375%		3.375%
Senior note public offering, amount | €	€ 650,000,000
Proceeds from term loan | €	€ 1,231,000,000
Senior notes | 3.950% senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.95%			3.95%		3.95%
Senior note public offering, amount | €	€ 600,000,000
Debt, interest accrual period	360 days

LONG-TERM OBLIGATIONS - SCHED_2

LONG-TERM OBLIGATIONS - SCHEDULE OF LINES OF CREDIT (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)renewal_period
2013 Credit Facility | Credit Facility
Line of Credit Facility [Line Items]
Outstanding Principal Balance	$ 2,340
Undrawn letters of credit	$ 3.8
Current commitment fee (as a percent)	0.125%
2013 Credit Facility | Credit Facility | LIBOR
Line of Credit Facility [Line Items]
Current margin over LIBOR (as a percent)	1.125%
2014 Credit Facility | Credit Facility
Line of Credit Facility [Line Items]
Outstanding Principal Balance	$ 0
Undrawn letters of credit	$ 6.2
Current commitment fee (as a percent)	0.125%
Optional renewal periods | renewal_period	2
2014 Credit Facility | Credit Facility | LIBOR
Line of Credit Facility [Line Items]
Current margin over LIBOR (as a percent)	1.125%
2013 Term Loan | Unsecured debt
Line of Credit Facility [Line Items]
Outstanding Principal Balance	$ 1,000
2013 Term Loan | Unsecured debt | LIBOR
Line of Credit Facility [Line Items]
Current margin over LIBOR (as a percent)	1.125%
2019 Term Loan | Unsecured debt
Line of Credit Facility [Line Items]
Outstanding Principal Balance	$ 1,300
2019 Term Loan | Unsecured debt | LIBOR
Line of Credit Facility [Line Items]
Current margin over LIBOR (as a percent)	0.80%

FAIR VALUE MEASUREMENTS - ASSET

FAIR VALUE MEASUREMENTS - ASSETS AND LIABILITIES MEASURED AT FAIR VALUE ON A RECURRING BASIS (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets:
Short-term investments	$ 18,400	$ 0
Fair Value, Measurements, Recurring | Level 1
Assets:
Short-term investments	0	0
Embedded derivative in lease agreement	0	0
Liabilities:
Acquisition-related contingent consideration	0	0
Redeemable noncontrolling interests	0	0
Fair Value, Measurements, Recurring | Level 1 | Interest rate swap agreements
Liabilities:
Interest rate swap agreements	0	0
Fair value of debt related to interest rate swap agreements	(19,000)	(31,300)
Fair Value, Measurements, Recurring | Level 2
Assets:
Short-term investments	18,400
Embedded derivative in lease agreement	0	0
Liabilities:
Acquisition-related contingent consideration	0	0
Redeemable noncontrolling interests	0	0
Fair Value, Measurements, Recurring | Level 2 | Interest rate swap agreements
Liabilities:
Interest rate swap agreements	21,800	33,800
Fair value of debt related to interest rate swap agreements	0	0
Fair Value, Measurements, Recurring | Level 3
Assets:
Short-term investments	0	0
Embedded derivative in lease agreement	11,300	11,500
Liabilities:
Acquisition-related contingent consideration	800	900
Redeemable noncontrolling interests	589,000	1,004,800
Fair Value, Measurements, Recurring | Level 3 | Interest rate swap agreements
Liabilities:
Interest rate swap agreements	0	0
Fair value of debt related to interest rate swap agreements	$ 0	$ 0

FAIR VALUE MEASUREMENTS - NARRA

FAIR VALUE MEASUREMENTS - NARRATIVE (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities at cost	$ 18,100,000
Marketable securities, unrealized gains	300,000
Business combination, contingent consideration arrangements, range of outcomes, value, low	0
Business combination, contingent consideration arrangements, range of outcomes, value, high	800,000
Asset impairments	18,100,000	$ 147,400,000
Long-term obligations	21,204,300,000		$ 21,159,900,000
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	21,500,000,000		21,100,000,000
Estimate of Fair Value Measurement | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	14,000,000,000		13,400,000,000
Estimate of Fair Value Measurement | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 7,500,000,000		$ 7,700,000,000

INCOME TAXES - NARRATIVE (Detai

INCOME TAXES - NARRATIVE (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact the ETR	$ 94,600,000	$ 93,700,000
Unrecognized tax benefits, increase resulting from current period tax positions	1,500,000
Unrecognized tax benefits, from foreign currency fluctuations	300,000
Unrecognized tax benefits, income tax penalties and interest accrued	20,300,000	$ 19,100,000
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	$ 2,800,000

INCOME TAXES - SCHEDULE OF PEN

INCOME TAXES - SCHEDULE OF PENALTIES AND INCOME TAX RELATED EXPENSES (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Penalties and income tax-related interest expense	$ 1.1	$ 1

STOCK-BASED COMPENSATION - NARR

STOCK-BASED COMPENSATION - NARRATIVE (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ESPP, discount rate (as a percent)	15.00%
Total unrecognized compensation expense	$ 3.2
Stock-based compensation expense	$ 42.5	$ 42.7
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected recognition of stock award compensation expense weighted average period in years	3 years
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years			3 years	3 years
Total unrecognized compensation expense	$ 20.4
Expected recognition of stock award compensation expense weighted average period in years	2 years
Performance grant, shares granted (in shares)	114,823	131,311	154,520		154,520
Stock-based compensation expense	$ 10.7
Performance Shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of potential target shares	0.00%
Performance Shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of potential target shares	200.00%
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected recognition of stock award compensation expense weighted average period in years	1 year
2007 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issuable under stock incentive plan	6,929,551
2007 Plan | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Total unrecognized compensation expense	$ 179.6
2007 Plan | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
2007 Plan | Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years

STOCK-BASED COMPENSATION - SUMM

STOCK-BASED COMPENSATION - SUMMARY OF STOCK-BASED COMPENSATION EXPENSE (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Stock-based compensation expense	$ 42.5	$ 42.7
Stock-based compensation expense capitalized as property and equipment	0.5	0.5
Property
Stock-based compensation expense	0.6	0.7
Service
Stock-based compensation expense	0.3	0.3
Selling, General and Administrative Expenses
Stock-based compensation expense	$ 41.6	$ 41.7

STOCK-BASED COMPENSATION - SU_2

STOCK-BASED COMPENSATION - SUMMARY OF THE COMPANY'S OPTION ACTIVITY (Details) - Employee Stock Option	3 Months Ended
	Mar. 31, 2019shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding as of January 1, 2019	4,257,470
Granted (in shares)	0
Exercised (in shares)	(314,847)
Forfeited (in shares)	0
Expired (in shares)	0
Outstanding as of March 31, 2019	3,942,623

STOCK-BASED COMPENSATION - SU_3

STOCK-BASED COMPENSATION - SUMMARY OF THE COMPANY'S RESTRICTED STOCK UNIT ACTIVITY (Details) - shares	3 Months Ended			12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Shares issued based upon achievement against performance metrics (in shares)				338,680
RSUs
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Outstanding as of January 1, 2019 (in shares)	1,649,973
Granted (in shares)	539,905
Vested (in shares)	(607,845)
Forfeited (in shares)	(13,599)
Outstanding as of March 31, 2019 (in shares)	1,568,434			1,649,973
Vested and deferred as of March 31, 2019 (in shares)	32,596
PSUs
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Outstanding as of January 1, 2019 (in shares)	624,511
Granted (in shares)	114,823
Vested (in shares)	(292,180)
Forfeited (in shares)	0
Outstanding as of March 31, 2019 (in shares)	447,154			624,511
Vested and deferred as of March 31, 2019 (in shares)	46,500
Vesting period	3 years			3 years	3 years
Three year performance grant, shares granted (in shares)	114,823	131,311	154,520		154,520
2007 Plan | RSUs
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Vesting period	4 years
2007 Plan | PSUs
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Vesting period	3 years

REDEEMABLE NONCONTROLLING INT_3

REDEEMABLE NONCONTROLLING INTERESTS (Details) ₨ / shares in Units, $ in Millions, ₨ in Billions	3 Months Ended
	Mar. 31, 2019USD ($)	Dec. 31, 2018	Mar. 31, 2018USD ($)	Mar. 31, 2019INR (₨)	Mar. 31, 2018₨ / shares	Apr. 21, 2016
Noncontrolling Interest [Line Items]
Adjustment to noncontrolling interest redemption value	$ 3.7		$ 17.5
Temporary equity, redemption price per share (in dollars per share) | ₨ / shares					₨ 216
Redemption consideration value	$ 425.7			₨ 29.4
Tata Teleservices Limited
Noncontrolling Interest [Line Items]
Percentage of ownership before transaction	50.00%
Percentage of ownership after transaction	79.00%	63.00%
IDFC
Noncontrolling Interest [Line Items]
Percentage of ownership before transaction	100.00%
Viom Transaction
Noncontrolling Interest [Line Items]
Percentage of interests acquired						51.00%
Adjustment to noncontrolling interest redemption value	$ 3.7		$ 17.5
Noncontrolling interest, ownership percentage by noncontrolling owners (as a percent)	21.00%	37.00%		21.00%

REDEEMABLE NONCONTROLLING INT_4

REDEEMABLE NONCONTROLLING INTERESTS - Changes in Redeemable Noncontrolling Interest (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Increase (Decrease) in Temporary Equity [Roll Forward]
Balance as of January 1,	$ 1,004.8	$ 1,126.2
Net loss attributable to noncontrolling interests	(3.7)	(28.1)
Adjustment to noncontrolling interest redemption value	3.7	17.5
Adjustment to noncontrolling interest due to merger/ due to purchase of interest	(425.7)	0
Foreign currency translation adjustment attributable to noncontrolling interests	9.9	(22.3)
Balance as of March 31,	589	1,065.2
Merger
Increase (Decrease) in Temporary Equity [Roll Forward]
Adjustment to noncontrolling interest due to merger/ due to purchase of interest	$ 0	$ (28.1)

EQUITY - NARRATIVE (Details)

EQUITY - NARRATIVE (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2011
Class of Stock [Line Items]
Proceeds from stock options	$ 27,200,000	$ 20,000,000
Shares repurchased (in shares)	10,557,000		10,557,000
Shares repurchased	$ 1,206,800,000		$ 1,206,800,000
Accrued dividend RSU	8,900,000
Dividends Declared and Paid
Class of Stock [Line Items]
Paid dividend RSU	$ 6,600,000
2011 Buyback
Class of Stock [Line Items]
Stock repurchase program, authorized amount					$ 1,500,000,000
Common stock repurchased (in shares)	0
Shares repurchased (in shares)	14,003,543
Shares repurchased	$ 1,400,000,000
2017 Buyback
Class of Stock [Line Items]
Stock repurchase program, authorized amount				$ 2,000,000,000
Common stock repurchased (in shares)	0

EQUITY - DISTRIBUTIONS (Details

EQUITY - DISTRIBUTIONS (Details) - USD ($) $ / shares in Units, $ in Millions	Apr. 26, 2019	Mar. 07, 2019	Jan. 14, 2019	Dec. 05, 2018	Apr. 27, 2018	Mar. 08, 2018	Jan. 22, 2018	Dec. 07, 2017	Mar. 31, 2019	Mar. 31, 2018
Dividends Payable [Line Items]
Aggregate Payment Amount on common stock									$ 377.1	$ 304.3
Payments of Ordinary Dividends, Preferred Stock and Preference Stock									$ 0	$ 18.9
Preferred Stock - Series B
Dividends Payable [Line Items]
Distribution per share, preferred stock (in dollars per share)							$ 13.75
Payments of Ordinary Dividends, Preferred Stock and Preference Stock							$ 18.9
Common Stock
Dividends Payable [Line Items]
Distribution per share, common stock (in dollars per share)		$ 0.9		$ 0.84		$ 0.75		$ 0.70
Aggregate Payment Amount on common stock			$ 370.5		$ 331.2			$ 300.2
Common Stock | Subsequent Event
Dividends Payable [Line Items]
Aggregate Payment Amount on common stock	$ 397.8

EARNINGS PER COMMON SHARE - SCH

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, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net income attributable to American Tower Corporation stockholders	$ 397,430	$ 285,200
Dividends on preferred stock	0	(9,400)
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION COMMON STOCKHOLDERS	$ 397,430	$ 275,800
Basic weighted average common shares outstanding (in shares)	441,351	435,124
Dilutive securities (in shares)	3,270	3,396
Diluted weighted average common shares outstanding (in shares)	444,621	438,520
Basic net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 0.90	$ 0.63
Diluted net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 0.89	$ 0.63

EARNINGS PER COMMON SHARE - S_2

EARNINGS PER COMMON SHARE - SCHEDULE OF SHARES EXCLUDED FROM COMPUTATION OF EARNINGS PER SHARE (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from dilutive effect	105	118
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from dilutive effect	0	0
Preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from dilutive effect	0	5,904

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - NARRATIVE (Details) ₨ in Millions	Dec. 05, 2016USD ($)	Dec. 05, 2016INR (₨)	Mar. 27, 2015USD ($)communications_siterenewal_period	Dec. 31, 2018USD ($)	Dec. 31, 2000tower	Mar. 31, 2019USD ($)towerrenewal_periodshares	Dec. 31, 2016tower
Verizon Transaction
Loss Contingencies [Line Items]
Capital leased assets, number of units (in number of communication sites) | communications_site			11,250
Right to lease, weighted average term			28 years
Aggregate purchase option price for towers | $			$ 5,000,000,000
Customer lease, initial term			10 years
Successive terms to renew lease (in numbers of terms) | renewal_period			8
Renewal term			5 years
AT&T Transaction
Loss Contingencies [Line Items]
Capital leased assets, number of units (in number of communication sites) | tower						2,270
Aggregate purchase option price for towers | $						$ 911,400,000
Successive terms to renew lease (in numbers of terms) | renewal_period						4
Renewal term						5 years
Operating lease, term of contract						27 years
Number of sites acquired life to date | tower						153
Purchase price accretion rate (per year)						10.00%
ALLTEL Transaction
Loss Contingencies [Line Items]
Capital leased assets, number of units (in number of communication sites) | tower					1,800
Aggregate purchase option price for towers | $						$ 10,400,000
Number of communications sites acquired (in number of towers) | tower							1,523
Average lease term (in years)					15 years
Number of remaining towers | tower							243
Cash purchase price per tower | $						$ 42,844
Purchase price of tower in shares of common stock (in shares) | shares						769
International [Member]
Loss Contingencies [Line Items]
Foreign income tax assessment | $				$ 129,000,000
INDIA
Loss Contingencies [Line Items]
Foreign income tax assessment	$ 69,800,000	₨ 4,750

ACQUISITIONS - SCHEDULE OF MERG

ACQUISITIONS - SCHEDULE OF MERGER AND ACQUISITION RELATED COSTS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Business Combinations [Abstract]
Acquisition and merger related expenses	$ 2	$ 1.4
Integration costs	4.1	$ 0.5
Payment received related to acquisition in France	$ 5.7

ACQUISITIONS - NARRATIVE (Detai

ACQUISITIONS - NARRATIVE (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)communications_site	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Revenue of acquiree since acquisition date	$ 0.4
Business combination pro forma information gross margin of acquiree since acquisition date actual	0.3
Accounts payable	130	$ 130.8
Other Acquisitions 2019
Business Acquisition [Line Items]
Aggregate purchase price	$ 95.3
Other Acquisitions 2019 | Communication Sites
Business Acquisition [Line Items]
Number of communications sites acquired (in number of towers) | communications_site	107

ACQUISITIONS - SUMMARY OF ALLOC

ACQUISITIONS - SUMMARY OF ALLOCATION OF THE PURCHASE PRICE (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)site	Dec. 31, 2018USD ($)
Asset Acquisition:
Current assets	$ 2,062.3	$ 2,385.1
Property and equipment	11,202.6	11,247.1
Intangible assets	11,042.8	11,174.3
Other non-current assets	279.1	962.6
Current liabilities	(4,411.9)	(4,689.9)
Deferred tax liability	(510.8)	(535.9)
Other non-current liabilities	(864.4)	(1,265.1)
Goodwill	5,538.2	5,501.9
Tenant-related intangible assets
Asset Acquisition:
Intangible assets	$ 7,934.8	8,009.3
Tenant-related intangible assets | Maximum
Asset Acquisition:
Estimated useful lives (in years)	20 years
Network location intangible assets
Asset Acquisition:
Intangible assets	$ 3,017.9	$ 3,075.4
Network location intangible assets | Maximum
Asset Acquisition:
Estimated useful lives (in years)	20 years
Other Acquisitions 2019
Asset Acquisition:
Current assets	$ 0.5
Property and equipment	15.5
Intangible assets	0
Other non-current assets	5.6
Current liabilities	(0.7)
Deferred tax liability	0
Other non-current liabilities	(8.8)
Net assets acquired	64.4
Goodwill	30.9
Fair value of net assets acquired	95.3
Debt assumed	0
Purchase price	$ 95.3
Other Acquisitions 2019 | Peru
Asset Acquisition:
Number of sites acquired | site	37
Other Acquisitions 2019 | Tenant-related intangible assets
Asset Acquisition:
Intangible assets	$ 46
Other Acquisitions 2019 | Tenant-related intangible assets | Maximum
Asset Acquisition:
Estimated useful lives (in years)	20 years
Other Acquisitions 2019 | Network location intangible assets
Asset Acquisition:
Intangible assets	$ 6.3
Other Acquisitions 2019 | Network location intangible assets | Maximum
Asset Acquisition:
Estimated useful lives (in years)	20 years

ACQUISITIONS - PRO FORMA INFORM

ACQUISITIONS - PRO FORMA INFORMATION (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Business Combinations [Abstract]
Pro forma revenues	$ 1,814.9	$ 1,844
Pro forma net income attributable to American Tower Corporation common stockholders	$ 397.9	$ 273.3
Pro forma net income per common share amounts:
Basic net income attributable to American Tower Corporation common stockholders (in dollars per share)	$ 0.90	$ 0.63
Diluted net income attributable to American Tower Corporation common stockholders (in dollars per share)	$ 0.89	$ 0.62

BUSINESS SEGMENTS (Details)

BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 1,813.4	$ 1,741.8
Segment operating expenses	542.5	518.9
Segment gross margin	1,270.9	1,225.6
Segment selling, general, administrative and development expense	117.8	124.5
Segment operating profit	1,153.1	1,101.1
Stock-based compensation expense	42.5	42.7
Other selling, general, administrative and development expense	38.7	38.7
Depreciation, amortization and accretion	436.9	446.3
Other expense	193.4	324.2
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	441.6	249.2
Total assets	38,926.8	34,372.7	$ 33,010.4
Impairment charges	18.1	147.4
Operating Expense
Segment Reporting Information [Line Items]
Stock-based compensation expense	0.9	1
Selling General Administrative And Development Expense
Segment Reporting Information [Line Items]
Stock-based compensation expense	41.6	41.7
TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net	0	2.7
Operating Segments | Property
Segment Reporting Information [Line Items]
Revenues	1,786	1,710.4
Segment operating expenses	532.4	506.7
Segment gross margin	1,253.6	1,206.4
Segment selling, general, administrative and development expense	114.4	121
Segment operating profit	1,139.2	1,085.4
Total assets	38,532.4	34,119
Operating Segments | Property | TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		2.7
Operating Segments | Property | U.S.
Segment Reporting Information [Line Items]
Revenues	986.3	931.4
Segment operating expenses	191.3	186.3
Segment gross margin	795	745.1
Segment selling, general, administrative and development expense	41.7	35.4
Segment operating profit	753.3	709.7
Total assets	22,160.9	18,894.7
Operating Segments | Property | U.S. | TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		0
Operating Segments | Property | Asia
Segment Reporting Information [Line Items]
Revenues	288.9	273
Segment operating expenses	178	157.9
Segment gross margin	110.9	115.1
Segment selling, general, administrative and development expense	26.6	44.2
Segment operating profit	84.3	70.9
Total assets	5,427.6	5,796.8
Operating Segments | Property | Asia | TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		0
Operating Segments | Property | EMEA
Segment Reporting Information [Line Items]
Revenues	177.5	174.2
Segment operating expenses	59.7	59.1
Segment gross margin	117.8	115.1
Segment selling, general, administrative and development expense	18.4	16.8
Segment operating profit	99.4	98.3
Total assets	3,637.5	3,343.4
Operating Segments | Property | EMEA | TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		0
Operating Segments | Property | Latin America
Segment Reporting Information [Line Items]
Revenues	333.3	331.8
Segment operating expenses	103.4	103.4
Segment gross margin	229.9	231.1
Segment selling, general, administrative and development expense	27.7	24.6
Segment operating profit	202.2	206.5
Total assets	7,306.4	6,084.1
Operating Segments | Property | Latin America | TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		2.7
Operating Segments | Services
Segment Reporting Information [Line Items]
Revenues	27.4	31.4
Segment operating expenses	10.1	12.2
Segment gross margin	17.3	19.2
Segment selling, general, administrative and development expense	3.4	3.5
Segment operating profit	13.9	15.7
Total assets	43.8	47
Operating Segments | Services | TV Azteca
Segment Reporting Information [Line Items]
Interest income, TV Azteca, net		0
Other
Segment Reporting Information [Line Items]
Stock-based compensation expense	42.5	42.7
Other selling, general, administrative and development expense	38.7	38.7
Depreciation, amortization and accretion	436.9	446.3
Other expense	193.4	324.2
Total assets	$ 350.6	$ 206.7

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) $ in Millions, ₨ in Billions	Apr. 22, 2019USD ($)	Apr. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018	Mar. 31, 2018USD ($)	Apr. 30, 2019INR (₨)	Mar. 31, 2019INR (₨)	Mar. 15, 2019
Subsequent Event [Line Items]
Loss on retirement of long-term obligations			$ 0.1		$ 0
Redemption consideration value			$ 425.7				₨ 29.4
Tata Teleservices Limited
Subsequent Event [Line Items]
Percentage of ownership before transaction			50.00%
Percentage of ownership after transaction			79.00%	63.00%
Senior notes
Subsequent Event [Line Items]
Redemption price percentage of principal								101.00%
5.050% senior notes | Senior notes
Subsequent Event [Line Items]
Long-term debt, stated interest rate (as a percent)			5.05%				5.05%
Subsequent Event
Subsequent Event [Line Items]
Redemption consideration value		$ 358.7				₨ 24.8
Percentage of ownership after transaction		92.00%
Subsequent Event | Tata Teleservices Limited
Subsequent Event [Line Items]
Percentage of ownership before transaction		100.00%
Subsequent Event | 5.050% senior notes | Senior notes
Subsequent Event [Line Items]
Long-term debt, stated interest rate (as a percent)	5.05%
Redemption price percentage of principal	103.005%
Aggregate redemption price	$ 726
Accrued and unpaid interest	5
Loss on retirement of long-term obligations	22.1
Prepayment consideration	$ 21

Uncategorized Items - amt-20190

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