Document And Entity Information - USD ($) $ in Billions	12 Months Ended
Document And Entity Information - USD ($) $ in Billions	Dec. 31, 2018	Feb. 21, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Entity Registrant Name	SBA COMMUNICATIONS CORP
Entity Central Index Key	0001034054
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		112,589,177
Entity Public Float			$ 18.8
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Trading Symbol	SBAC

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 143,444	$ 68,783
Restricted cash	32,464	32,924
Accounts receivable, net	111,035	90,673
Costs and estimated earnings in excess of billings on uncompleted contracts	23,785	17,437
Prepaid expenses and other current assets	63,126	49,716
Total current assets	373,854	259,533
Property and equipment, net	2,786,355	2,812,346
Intangible assets, net	3,331,465	3,598,131
Other assets	722,033	650,195
Total assets	7,213,707	7,320,205
Current liabilities:
Accounts payable	34,308	33,334
Accrued expenses	63,665	69,862
Current maturities of long-term debt	941,728	20,000
Deferred revenue	108,054	97,969
Accrued interest	48,722	48,899
Other current liabilities	9,802	8,841
Total current liabilities	1,206,279	278,905
Long-term liabilities:
Long-term debt, net	8,996,825	9,290,686
Other long-term liabilities	387,426	349,728
Total long-term liabilities	9,384,251	9,640,414
Shareholders' deficit:
Preferred stock - par value $.01, 30,000 shares authorized, no shares issued or outstanding
Common stock - Class A, par value $.01, 400,000 shares authorized, 112,433 Common stock - Class A, par value $.01, 400,000 shares authorized, 112,433 and 116,446 shares issued and outstanding at December 31, 2018 and December 31, 2017, respectively	1,124	1,164
Additional paid-in capital	2,270,326	2,167,470
Accumulated deficit	(5,136,368)	(4,388,288)
Accumulated other comprehensive loss, net	(511,905)	(379,460)
Total shareholders' deficit	(3,376,823)	(2,599,114)
Total liabilities and shareholders' deficit	$ 7,213,707	$ 7,320,205

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Consolidated Balance Sheets [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	30,000,000	30,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock - Class A, par value	$ 0.01	$ 0.01
Common stock - Class A, shares authorized	400,000,000	400,000,000
Common stock - Class A, shares issued	112,433,000	116,446,000
Common stock - Class A, shares outstanding	112,433,000	116,446,000

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Site leasing	$ 1,740,434	$ 1,623,173	$ 1,538,070
Site development	125,261	104,501	95,055
Total revenues	1,865,695	1,727,674	1,633,125
Cost of revenues (exclusive of depreciation, accretion, and amortization shown below):
Cost of site leasing	372,296	359,527	342,215
Cost of site development	96,499	86,785	78,682
Selling, general, and administrative	142,526	130,697	143,349
Acquisition related adjustments and expenses	10,961	12,367	13,140
Asset impairment and decommission costs	27,134	36,697	30,242
Depreciation, accretion, and amortization	672,113	643,100	638,189
Total operating expenses	1,321,529	1,269,173	1,245,817
Operating income	544,166	458,501	387,308
Other income (expense):
Interest income	6,731	11,337	10,928
Interest expense	(376,217)	(323,749)	(329,171)
Non-cash interest expense	(2,640)	(2,879)	(2,203)
Amortization of deferred financing fees	(20,289)	(21,940)	(21,136)
Loss from extinguishment of debt, net	(14,443)	(1,961)	(52,701)
Other (expense) income, net	(85,624)	(2,418)	94,278
Total other expense, net	(492,482)	(341,610)	(300,005)
Income before provision for income taxes	51,684	116,891	87,303
Provision for income taxes	(4,233)	(13,237)	(11,065)
Net income	$ 47,451	$ 103,654	$ 76,238
Net income per common share:
Basic	$ 0.41	$ 0.86	$ 0.61
Diluted	$ 0.41	$ 0.86	$ 0.61
Weighted average common shares outstanding:
Basic	114,909	119,860	124,448
Diluted	116,515	121,022	125,144

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Consolidated Statements of Comprehensive Income (Loss) [Abstract]
Net income	$ 47,451	$ 103,654	$ 76,238
Foreign currency translation adjustments	(132,445)	(9,276)	131,861
Comprehensive (loss) income	$ (84,994)	$ 94,378	$ 208,099

Consolidated Statement of Shareholders' Deficit - USD ($) $ in Thousands	Common Stock [Member] Class A Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]	Total
BALANCE at Dec. 31, 2015	$ 1,257	$ 1,962,713	$ (3,168,069)	$ (502,045)	$ (1,706,144)
BALANCE, Shares at Dec. 31, 2015	125,743,000
Net income			76,238		76,238
Common stock issued in connection with stock purchase/option plans	$ 6	14,404			14,410
Common stock issued in connection with stock purchase/option plans, Shares	602,000
Non-cash stock compensation		33,403			33,403
Repurchase and retirement of common stock	$ (53)		(545,636)		(545,689)
Repurchase and retirement of common stock, Shares	(5,341,000)
Foreign currency translation adjustments				131,861	131,861
BALANCE at Dec. 31, 2016	$ 1,210	2,010,520	(3,637,467)	(370,184)	(1,995,921)
BALANCE, Shares at Dec. 31, 2016	121,004,000
Net income			103,654		103,654
Common stock issued in connection with stock purchase/option plans	$ 8	54,798			54,806
Common stock issued in connection with stock purchase/option plans, Shares	812,000
Non-cash stock compensation		38,844			38,844
Common stock issued in connection with acquisitions	$ 5	63,308			63,313
Common stock issued in connection with acquisitions, Shares	488,000
Repurchase and retirement of common stock	$ (59)		(854,475)		(854,534)
Repurchase and retirement of common stock, Shares	(5,858,000)
Foreign currency translation adjustments				(9,276)	(9,276)
BALANCE at Dec. 31, 2017	$ 1,164	2,167,470	(4,388,288)	(379,460)	$ (2,599,114)
BALANCE, Shares at Dec. 31, 2017	116,446,000				116,446,000
Net income			47,451		$ 47,451
Common stock issued in connection with stock purchase/option plans	$ 10	59,716			59,726
Common stock issued in connection with stock purchase/option plans, Shares	962,000
Non-cash stock compensation		43,140			43,140
Repurchase and retirement of common stock	$ (50)		(795,531)		(795,581)
Repurchase and retirement of common stock, Shares	(4,975,000)
Foreign currency translation adjustments				(132,445)	(132,445)
BALANCE at Dec. 31, 2018	$ 1,124	$ 2,270,326	$ (5,136,368)	$ (511,905)	$ (3,376,823)
BALANCE, Shares at Dec. 31, 2018	112,433,000				112,433,000

Consolidated Statements of Cash Flows - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 47,451	$ 103,654	$ 76,238
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, accretion, and amortization	672,113	643,100	638,189
Non-cash asset impairment and decommission costs	26,192	32,423	25,693
Non-cash compensation expense	42,327	38,249	32,915
Amortization of deferred financing fees	20,289	21,940	21,136
Loss (gain) on remeasurement of U.S. denominated intercompany loan	89,101	8,754	(90,030)
Provision for doubtful accounts	551	2,909	22,516
Loss from extinguishment of deb, net	14,087	1,961	52,701
Other non-cash items reflected in the Statements of Operations	(14,586)	(4,850)	(1,225)
Changes in operating assets and liabilities, net of acquisitions:
AR and costs and est. earnings in excess of billings on uncompleted contracts, net	(29,427)	(20,893)	(7,270)
Prepaid expenses and other assets	(38,040)	(16,888)	(40,289)
Accounts payable and accrued expenses	(3,021)	3,555	(10,516)
Other liabilities	23,581	4,556	22,467
Net cash provided by operating activities	850,618	818,470	742,525
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions	(451,829)	(441,547)	(276,835)
Capital expenditures	(149,812)	(147,044)	(139,982)
Purchase of investments	(156,983)	(397)	(100)
Proceeds from sale of investments	150,890	231	712
Other investing activities	(10,613)	(16,350)	(12,030)
Net cash used in investing activities	(618,347)	(605,107)	(428,235)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings under Revolving Credit Facility	1,120,000	525,000	580,000
Repayments under Revolving Credit Facility	(835,000)	(875,000)	(190,000)
Repayment of Term Loans	(1,947,000)	(20,000)	(20,000)
Proceeds from issuance of Term Loans, net of fees	2,377,218
Proceeds from issuance of Senior Notes, net of fees		741,108	1,078,123
Proceeds from issuance of Tower Securities, net of fees	631,466	749,764	690,475
Repayment of Tower Securities	(755,000)	(610,000)	(550,000)
Repurchase and retirement of common stock	(795,581)	(854,534)	(545,689)
Other financing activities	55,360	49,088	8,394
Net cash used in financing activities	(148,537)	(294,574)	(288,557)
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	(9,729)	(464)	13,618
NET CHANGE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	74,005	(81,675)	39,351
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH:
Beginning of year	104,295	185,970	146,619
End of year	178,300	104,295	185,970
Cash paid during the period for:
Interest	376,628	319,562	338,409
Income taxes	21,645	14,653	9,655
SUPPLEMENTAL CASH FLOW INFORMATION OF NON-CASH ACTIVITIES:
Assets acquired through capital leases	$ 1,039	$ 254	1,386
Common stock issued in connection with acquisitions		63,313
5.625% Senior Notes [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment for the redemption of Senior Notes			(514,065)
5.75% Senior Notes [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment for the redemption of Senior Notes			$ (825,795)

Consolidated Statements of Cash Flows (Parenthetical)	Dec. 31, 2018	Dec. 31, 2016	Sep. 28, 2012	Jul. 13, 2012
5.625% Senior Notes [Member]
Debt instrument stated percentage	5.625%	5.625%	5.625%
5.75% Senior Notes [Member]
Debt instrument stated percentage	5.75%	5.75%		5.75%

General	12 Months Ended
General	Dec. 31, 2018
General [Abstract]
General	1.GENERAL SBA Communications Corporation (the “Company” or “SBAC”) was incorporated in the State of Florida in March 1997. The Company is a holding company that holds all of the outstanding capital stock of SBA Telecommunications, LLC (“Telecommunications”). Telecommunications is a holding company that holds the outstanding capital stock of SBA Senior Finance, LLC (“SBA Senior Finance”), and other operating subsidiaries which are not a party to any loan agreement. SBA Senior Finance is a holding company that holds, directly or indirectly, the equity interest in certain subsidiaries that issued the Tower Securities (see Note 12) and certain subsidiaries that were not involved in the issuance of the Tower Securities. With respect to the subsidiaries involved in the issuance of the Tower Securities, SBA Senior Finance is the sole member of SBA Holdings, LLC and SBA Depositor, LLC. SBA Holdings, LLC is the sole member of SBA Guarantor, LLC. SBA Guarantor, LLC directly or indirectly holds all of the capital stock of the companies referred to as the “Borrowers” under the Tower Securities. With respect to subsidiaries not involved in the issuance of the Tower Securities, SBA Senior Finance holds all of the membership interests in SBA Senior Finance II, LLC (“SBA Senior Finance II”) and certain non-operating subsidiaries. SBA Senior Finance II holds, directly or indirectly, all the capital stock of certain international subsidiaries and certain other tower companies (known as “Tower Companies”). SBA Senior Finance II also holds, directly or indirectly, all the capital stock and/or membership interests of certain other subsidiaries involved in providing services, including SBA Network Services, LLC (“Network Services”) as well as SBA Network Management, Inc. (“Network Management”) which manages and administers the operations of the Borrowers. As of December 31, 2018, the Company owned and operated wireless towers in the United States and its territories. In addition, the Company owned towers in Argentina, Brazil, Canada, Chile, Colombia, Costa Rica, Ecuador, El Salvador, Guatemala, Nicaragua, Panama, and Peru. Space on these towers is leased primarily to wireless service providers. As of December 31, 2018, the Company owned and operated 29,578 towers of which 16,263 are domestic and 13,315 are international.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Summary of Significant Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

A summary of the significant accounting policies applied in the preparation of the accompanying consolidated financial statements is as follows:

Principles of Consolidation

The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the Company and its majority and wholly-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. The significant estimates made by management relate to the allowance for doubtful accounts, the costs and revenue relating to the Company’s construction contracts, stock-based compensation assumptions, valuation allowance related to deferred tax assets, fair value of long-lived assets, the useful lives of towers and intangible assets, anticipated property tax assessments, fair value of investments and asset retirement obligations. Management develops estimates based on historical experience and on various assumptions about the future that are believed to be reasonable based on the information available. These estimates ultimately may differ from actual results and such differences could be material.

Cash and Cash Equivalents

Cash and cash equivalents consist primarily of cash in banks, money market funds, commercial paper, highly liquid short-term investments, and other marketable securities with an original maturity of three months or less at the time of purchase. These investments are carried at cost, which approximates fair value.

Restricted Cash

The Company classifies all cash pledged as collateral to secure certain obligations and all cash whose use is limited as restricted cash. This includes cash held in escrow to fund certain reserve accounts relating to the Tower Securities as well as for payment and performance bonds and surety bonds issued for the benefit of the Company in the ordinary course of business, as well as collateral associated with workers’ compensation plans (see Note 4).

Investments

Investment securities with original maturities of more than three months but less than one year at time of purchase are considered short-term investments. The Company’s short-term investments primarily consist of certificates of deposit with maturities of less than a year. Investment securities with maturities of more than a year are considered long-term investments and are classified in other assets on the accompanying Consolidated Balance Sheets. Long-term investments primarily consist of U.S. Treasuries, mutual funds, and preferred securities. Gross purchases and sales of the Company’s investments are presented within “Cash flows from investing activities” on the Company’s Consolidated Statements of Cash Flows.

The Company accounts for its investments in privately held companies under the equity method. The Company evaluates its investments for impairment at least annually. The Company determines the fair value of its investments by considering available evidence, including general market conditions, the investee’s financial condition, near-term prospects, market comparables and subsequent rounds of financing. The Company measures and records its investments at fair value when they are deemed to be other-than-temporarily impaired. The Company did not recognize any impairment loss associated with its investments during the years ended December 31, 2018, 2017, and 2016.

During the years ended December 31, 2018 and 2017, the Company received proceeds related to the sale or maturity of investments of $150.9 million and $0.2 million, respectively. During the year ended December 31, 2018 and 2017, no gain or loss was recorded related to the sale or maturity of investments. The proceeds are reflected in Net cash used in investing activities on the Consolidated Statements of Cash Flows. The aggregate carrying value of the Company’s investments was approximately $14.6 million and $8.6 million as of December 31, 2018 and 2017, respectively, and is classified within prepaid and other current assets and other assets on the Company’s consolidated balance sheets.

Property and Equipment

Property and equipment are recorded at cost or at estimated fair value (in the case of acquired properties), adjusted for asset impairment and estimated asset retirement obligations. Costs for self-constructed towers include direct materials and labor, indirect costs and capitalized interest. Approximately $0.9 million, $1.1 million, and $1.0 million of interest cost was capitalized in 2018, 2017 and 2016, respectively.

Depreciation on towers and related components is provided using the straight-line method over the estimated useful lives, not to exceed the minimum lease term of the underlying ground lease. The Company defines the minimum lease term as the shorter of the period from lease inception through the end of the term of all tenant lease obligations in existence at ground lease inception, including renewal periods, or the ground lease term, including renewal periods. If no tenant lease obligation exists at the date of ground lease inception, the initial term of the ground lease is considered the minimum lease term. Leasehold improvements are amortized on a straight-line basis over the shorter of the useful life of the improvement or the minimum lease term of the lease. For all other property and equipment, depreciation is provided using the straight-line method over the estimated useful lives.

The Company performs ongoing evaluations of the estimated useful lives of its property and equipment for depreciation purposes. The estimated useful lives are determined and continually evaluated based on the period over which services are expected to be rendered by the asset. If the useful lives of assets are reduced, depreciation may be accelerated in future years. Property and equipment under capital leases are amortized on a straight-line basis over the term of the lease or the remaining estimated life of the leased property, whichever is shorter, and the related amortization is included in depreciation expense. Expenditures for maintenance and repair are expensed as incurred.

Asset classes and related estimated useful lives are as follows:



Towers and related components	3 - 15 years
Furniture, equipment and vehicles	2 - 7 years
Buildings and improvements	10 - 30 years

Betterments, improvements, and significant repairs, which increase the value or extend the life of an asset, are capitalized and depreciated over the estimated useful life of the respective asset. Changes in an asset’s estimated useful life are accounted for prospectively, with the book value of the asset at the time of the change being depreciated over the revised remaining useful life. There has been no material impact for changes in estimated useful lives for any years presented.

Deferred Financing Fees

Financing fees related to the issuance of debt have been deferred and are being amortized using the effective interest rate method over the expected duration of the related indebtedness (see Note 12). For all of the Company’s debt, except for the Revolving Credit Facility where the debt issuance costs are being presented as an asset on the accompanying Consolidated Balance Sheet, debt issuance costs are presented on the balance sheet as a direct deduction from the related debt liability rather than as an asset.

Deferred Lease Costs

The Company defers certain initial direct costs associated with the origination of tenant leases and lease amendments and amortizes these costs over the initial lease term or over the lease term remaining if related to a lease amendment. Such deferred costs were approximately $11.3 million, $11.0 million, and $10.2 million in 2018, 2017, and 2016, respectively. Amortization expense was $12.2 million, $13.1 million, and $11.3 million for the years ended December 31, 2018, 2017 and 2016, respectively, and is included in cost of site leasing on the accompanying Consolidated Statements of Operations. As of December 31, 2018 and 2017, unamortized deferred lease costs were $27.0 million and $27.7 million, respectively, and are included in other assets on the accompanying Consolidated Balance Sheets.

Effective January 1, 2019, the Company adopted ASU 2016-02, Leases, which changed how deferred lease costs are calculated. Refer to “Recent Accounting Pronouncements Not Yet Adopted” for further changes related to the adoption of this guidance.

Intangible Assets

The Company classifies as intangible assets the fair value of current leases in place at the acquisition date of towers and related assets (referred to as the “Current contract intangibles”), and the fair value of future tenant leases anticipated to be added to the acquired towers (referred to as the “Network location intangibles”). These intangibles are estimated to have a useful life consistent with the useful life of the related tower assets, which is typically 15 years. For all intangible assets, amortization is provided using the straight-line method over the estimated useful lives as the benefit associated with these intangible assets is anticipated to be derived evenly over the life of the asset.

Impairment of Long-Lived Assets

The Company evaluates its individual long-lived and related assets with finite lives for indicators of impairment to determine when an impairment analysis should be performed. The Company evaluates its tower assets and Current contract intangibles at the tower level, which is the lowest level for which identifiable cash flows exists. The Company evaluates its Network location intangibles for impairment at the tower leasing business level whenever indicators of impairment are present. The Company has established a policy to at least annually evaluate its tower assets and Current contract intangibles for impairment.

The Company records an impairment charge when an investment in towers or related assets has been impaired, such that future undiscounted cash flows would not recover the then current carrying value of the investment in the tower and related intangible. If the future undiscounted cash flows are lower than the carrying value of the investment in the tower and related intangible, the Company calculates future discounted cash flows and compares those amounts to the carrying value. The Company records an impairment charge for any amounts lower than the carrying value. Estimates and assumptions inherent in the impairment evaluation include, but are not limited to, general market and economic conditions, historical operating results, geographic location, lease-up potential and expected timing of lease-up. In addition, the Company makes certain assumptions in determining an asset’s fair value for the purpose of calculating the amount of an impairment charge.

The Company recognized impairment charges of $27.1 million, $36.7 million, and $30.2 million for the years ended December 31, 2018, 2017 and 2016, respectively. Refer to Note 3 for further detail of these amounts.

Fair Value Measurements

The Company determines the fair market values 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. The following three levels of inputs 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.

Revenue Recognition and Accounts Receivable

Revenue from site leasing is recognized on a straight-line basis over the current term of the related lease agreements, which are generally five to ten years. Receivables recorded related to the straight-line impact of site leases are reflected in other assets on the Consolidated Balance Sheets. Rental amounts received in advance are recorded as deferred revenue on the Consolidated Balance Sheets. Revenues from site leasing represent 93% of the Company’s total revenues.

Site development projects in which the Company performs consulting services include contracts on a fixed price basis that are billed at contractual rates. Revenue is recognized over time based on milestones achieved, which are determined based on costs incurred. Amounts billed in advance (collected or uncollected) are recorded as deferred revenue on the Consolidated Balance Sheets.

Revenue from construction projects is recognized over time, determined by the percentage of cost incurred to date compared to management’s estimated total cost for each contract. This method is used because management considers total cost to be the best available measure of progress on the contracts. These amounts are based on estimates, and the uncertainty inherent in the estimates initially is reduced as work on the contracts nears completion. Refer to Note 9 for further detail of costs and estimated earnings in excess of billings on uncompleted contracts. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses are determined to be probable.

The site development segment represents approximately 7% of the Company’s total revenues. The Company accounts for site development revenue in accordance with ASC 606, Revenue from Contracts with Customers, which was adopted on January 1, 2018 by applying the modified retrospective transition method. Payment terms do not result in any significant financing arrangements. Furthermore, these contracts do not typically include variable consideration; therefore, the transaction price that is recognized over time is generally the amount of the total contract. The cumulative effect of initially applying the new revenue standard had no impact on the Company’s financial results. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The adoption of the new standard will have no impact to net income on an ongoing basis.

The accounts receivable balance was $111.0 million and $90.7 million as of December 31, 2018 and 2017, respectively, of which $27.1 million and $20.8 million related to the site development segment as of December 31, 2018 and 2017, respectively. Refer to Note 18 for further detail of the site development segment.

Allowance for Doubtful Accounts

The Company performs periodic credit evaluations of its customers. The Company monitors collections and payments from its customers and maintains a provision for estimated credit losses based upon historical experience, specific customer collection issues identified, and past due balances as determined based on contractual terms. Interest is charged on outstanding receivables from customers on a case by case basis in accordance with the terms of the respective contracts or agreements with those customers. Amounts determined to be uncollectible are written off against the allowance for doubtful accounts in the period in which uncollectibility is determined to be probable.

The following is a rollforward of the allowance for doubtful accounts:



	For the year ended December 31,
	2018		2017		2016

		(in thousands)
Beginning balance	$	26,481	$	24,518	$	1,681
Provision for doubtful accounts		551		2,909		22,516
Write-offs, net of recoveries		(591)		(647)		(614)
Currency translation adjustment		(2,561)		(299)		935
Ending balance	$	23,880	$	26,481	$	24,518

On June 20, 2016, Oi, S.A. (“Oi”), the Company’s largest customer in Brazil, filed a petition for judicial reorganization in Brazil. Prior to the filing of the reorganization petition, Oi was current in all payment obligations to the Company through April 30, 2016. Due to the uncertainty surrounding the recoverability of amounts owed by Oi relating to services provided prior to the date of Oi’s petition, the Company has recorded a $16.5 million bad debt provision (the “Oi reserve”) which covers amounts owed or potentially owed by Oi as of the filing date. The Oi reserve was recorded in Selling, general, and administrative expense on the consolidated statement of operations for the year ended December 31, 2016. Under Brazilian law governing judicial reorganizations, the contracts governing post-petition obligations such as tower rents remain unchanged, and debtors do not have the ability to reject or terminate the contracts other than pursuant to their original terms. Since the filing, the Company has received all rental payments due in connection with obligations of Oi accruing post-petition. On January 8, 2018, Oi’s reorganization plan was approved by the Brazilian courts and Oi is expected to fully resolve all its pre-petition obligations in accordance with the terms of the plan, which includes a 10% reduction in the receivable and four annual installment payments beginning in December 2019.

Cost of Revenue

Cost of site leasing revenue includes ground lease rent, property taxes, amortization of deferred lease costs, maintenance and other tower operating expenses. All ground lease rental obligations due to be paid out over the lease term, including fixed escalations, are recorded on a straight-line basis over the minimum lease term. Liabilities recorded related to the straight-lining of ground leases are reflected in other long-term liabilities on the Consolidated Balance Sheets. Cost of site development revenue includes the cost of materials, salaries and labor costs, including payroll taxes, subcontract labor, vehicle expense and other costs directly and indirectly related to the projects. All costs related to site development projects are recognized as incurred.

Income Taxes

The Company recognizes deferred tax assets and liabilities for the estimated future tax consequences attributable to differences between the financial reporting and tax bases of existing assets and liabilities. Deferred tax assets and liabilities are measured using tax rates in effect for the year in which the temporary differences are expected to reverse. A valuation allowance is recorded to reduce the carrying amounts of deferred tax assets if it is "more-likely-than-not" that those assets will not be realized. The Company considers many factors when assessing the likelihood of future realization, including the Company's recent cumulative earnings by taxing jurisdiction, expectations of future taxable income, prudent and feasible tax planning strategies that are available, the carryforward periods available to the Company for tax reporting purposes and other relevant factors.

The Company began operating as a REIT for federal income tax purposes effective January 1, 2016. As a REIT, the Company generally is not subject to corporate level federal income tax on taxable income it distributes to its stockholders as long as it meets the organizational and operational requirements under the REIT rules. However, certain subsidiaries have made an election with the IRS to be treated as a taxable REIT subsidiary (“TRS”) in conjunction with the Company's REIT election. The TRS elections permit SBA to engage in certain business activities in which the REIT may not engage directly, so long as these activities are conducted in entities that elect to be treated as TRSs under the Code. A TRS is subject to federal and state income taxes on the income from these activities. Additionally, the Company has included in TRSs the Company’s tower operations in most foreign jurisdictions; however, the REIT holds selected tower assets in Puerto Rico and USVI. Those operations will continue to be subject to foreign taxes in the jurisdiction in which such assets and operations are located regardless of whether they are included in a TRS.

The Company will continue to file separate federal tax returns for the REIT and TRS for the year ended December 31, 2018. The REIT had taxable income and utilized net operating losses (“NOLs”) to offset its 2018 distribution requirement. Some of our TRSs generated NOLs which will be carried forward to use in future years. The deferred tax asset generated by the NOLs are fully reserved by a valuation allowance.

The Company records a liability for unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in a tax return if applicable. The Company has not identified any tax exposures that require a reserve. To the extent that the Company records unrecognized tax exposures, any related interest and penalties will be recognized as interest expense in the Company’s Consolidated Statements of Operations.

Stock-Based Compensation

The Company measures and recognizes compensation expense for all share-based payment awards made to employees and directors, including stock options, restricted stock units and employee stock purchases under employee stock purchase plans. The Company records compensation expense, for stock options and restricted stock units on a straight-line basis over the vesting period. Compensation expense for employee stock options is based on the estimated fair value of the options on the date of the grant using the Black-Scholes option-pricing model. Compensation expense for restricted stock units is based on the fair market value of the units awarded at the date of the grant.

Asset Retirement Obligations

The Company has entered into ground leases for the land underlying the majority of the Company’s towers. A majority of these leases require the Company to restore land interests to their original condition upon termination of the ground lease.

The Company recognizes asset retirement obligations in the period in which they are incurred, if a reasonable estimate of a fair value can be made, and accretes such liability through the obligation’s estimated settlement date. The associated asset retirement costs are capitalized as part of the carrying amount of the related tower fixed assets, and over time, the liability is accreted to its present value each period and the capitalized cost is depreciated over the estimated useful life of the tower.

As of December 31, 2018 and 2017, the asset retirement obligation was $9.9 million and $7.2 million, respectively, and is included in other long-term liabilities on the Consolidated Balance Sheets. Upon settlement of the obligations, any difference between the cost to retire an asset and the recorded liability is recorded in the Consolidated Statements of Operations. In determining the measurement of the asset retirement obligations, the Company considered the nature and scope of the contractual restoration obligations contained in the Company’s ground leases, the historical retirement experience as an indicator of future restoration probabilities, intent in renewing existing ground leases through lease termination dates, current and future value and timing of estimated restoration costs and the credit adjusted risk-free rate used to discount future obligations.

Comprehensive Income (Loss)

Comprehensive income (loss) is defined as the change in equity (net assets) of a business enterprise during a period from transactions and other events and circumstances from non-owner sources, and is comprised of net income (loss) and other foreign currency adjustments.

Foreign Currency Translation

All assets and liabilities of foreign subsidiaries that do not utilize the U.S. dollar as its functional currency are translated at period-end rates of exchange, while revenues and expenses are translated at monthly average rates of exchange prevailing during the year. Unrealized remeasurement gains and losses are reported as foreign currency translation adjustments through Accumulated Other Comprehensive Loss in the accompanying Consolidated Statement of Shareholders’ Deficit.

For foreign subsidiaries where the U.S. dollar is the functional currency, monetary assets and liabilities of such subsidiaries, which are not denominated in U.S. dollars, are remeasured at exchange rates in effect at the balance sheet date, and revenues and expenses are remeasured at monthly average rates prevailing during the year. Unrealized translation gains and losses are reported as other income (expense), net in the Consolidated Statement of Operations.

Acquisitions

In January 2017, the FASB issued ASU 2017-01, Clarifying the Definition of a Business. ASU 2017-01 provides revised guidance to determine when an acquisition meets the definition of a business or when the acquisition should be accounted for as an asset acquisition. The Company adopted this standard effective January 1, 2017 and all changes are being accounted for prospectively. The adoption of ASU 2017-01 did not have a material impact on the Company’s unaudited consolidated financial statements and related disclosures.

Under the new standard, the Company’s acquisitions will generally qualify for asset acquisition treatment under ASC 360, Property, Plant, and Equipment, rather than business combination treatment under ASC 805 Business Combinations. For acquisitions, the aggregate purchase price is allocated on a relative fair value basis to towers and related intangible assets. The fair values of these net assets acquired are based on management’s estimates and assumptions, as well as other information compiled by management, including valuations that utilize customary valuation procedures and techniques. The fair value estimates are based on available historical information and on future expectations and assumptions deemed reasonable by management at the time. For acquisitions, if the actual results differ from the estimates and judgments used in these fair values, the amounts recorded in the consolidated financial statements could be subject to a possible impairment of the intangible assets, or require acceleration of the amortization expense of intangible assets in subsequent periods. For acquisitions, external, direct transaction costs will be capitalized as a component of the cost of the asset acquired. The Company will continue to expense internal acquisition costs as incurred. For business combinations, the estimates of the fair value of the assets acquired and liabilities assumed at the date of an acquisition are subject to adjustment during the measurement period (up to one year from the particular acquisition date). During the measurement period, the Company will adjust assets and/or liabilities if new information is obtained about facts and circumstances that existed as of the acquisition date that, if known, would have resulted in a revised estimated value of those assets and/or liabilities as of that date. As of December 31, 2018, there were no purchase price allocations that were preliminary.

In connection with certain acquisitions, the Company may agree to pay contingent consideration (or earnouts) in cash or stock if the communication sites or businesses that are acquired meet or exceed certain performance targets over a period of one to three years after they have been acquired. The Company accrues for contingent consideration in connection with business combinations at fair value as of the date of the acquisition. All subsequent changes in fair value of contingent consideration payable in cash are recorded through Consolidated Statements of Operations. Contingent consideration in connection with asset acquisitions will be recognized at the time when the contingency is resolved or becomes payable and will increase the cost basis of the assets acquired.

Intercompany Loans Subject to Remeasurement

The Company has two wholly owned subsidiaries, Brazil Shareholder I, LLC, a Florida limited liability company, and SBA Torres Brasil, Limitada, a limited liability company existing under the laws of the Republic of Brazil, which have entered into intercompany loan agreements pursuant to which the entities may from time to time agree to lend/borrow amounts under the terms of each agreement. The first agreement entered into in November 2014 was for $750.0 million and was created to fund the acquisition of 1,641 towers in Brazil. The second agreement entered into in December 2017 was for $500.0 million and was created to fund the acquisition of 941 towers in Brazil.

In accordance with Accounting Standards Codification (ASC) 830, the Company remeasures foreign denominated intercompany loans with the corresponding change in the balance being recorded in Other income (expense), net in the Consolidated Statement of Operations as settlement is anticipated or planned in the foreseeable future. For the years ended December 31, 2018, 2017, and 2016, the Company recorded a $89.1 million loss, a $8.8 million loss, and a $90.0 million gain, respectively, on the remeasurement of intercompany loans due to changes in foreign exchange rates. As of December 31, 2018 and 2017, the aggregate amount outstanding under the two intercompany loan agreements with the Company’s Brazilian subsidiary was $536.9 million and $560.9 million, respectively.

Recent Accounting Pronouncements Not Yet Adopted

In February 2016, the FASB issued ASU 2016-02, Leases. The standard requires lessees to recognize a right-of-use asset and a lease liability, initially measured at the present value of the lease payments for all leases with a term greater than 12 months. The accounting for lessors remains largely unchanged from existing guidance. The Company has adopted this standard as of January 1, 2019. This guidance will have a material impact on the Company’s consolidated balance sheet due to the recognition of lease liabilities for its ground leases of approximately $2.3 billion to $2.7 billion. Adoption of this guidance will not have a significant impact on the Company’s lease classification, a material impact on its consolidated statement of operations, or a notable impact on its liquidity. Additionally, the standard will have no impact on the Company’s debt-covenant compliance under its current agreements.

In July 2018, the FASB issued additional guidance on the accounting for leases. The guidance provides companies with another transition method that allows entities to recognize a cumulative-effect adjustment to the opening balance of retained earnings as of the date of adoption. Under this method, previously presented years’ financial positions and results are not adjusted. The Company adopted this alternative transition method. The new guidance also provides lessors with a practical expedient, by class of underlying asset, to not separate non-lease components from the associated lease component if (1) the non-lease components would otherwise be accounted for under the new revenue recognition standard, (2) both the timing and pattern of transfer are the same for the non-lease components and associated lease component, and (3) if accounted for separately, the lease component would be classified as an operating lease. The Company adopted this practical expedient in its accounting for leases.

Fair Value Measurements

12 Months Ended

Dec. 31, 2018

Fair Value Measurements [Abstract]

Fair Value Measurements

3.FAIR VALUE MEASUREMENTS

Items Measured at Fair Value on a Recurring Basis— The Company’s earnout liabilities related to business combinations are measured at fair value on a recurring basis using Level 3 inputs and are recorded in Accrued expenses in the accompanying Consolidated Balance Sheets. Changes in estimates are recorded in Acquisition related adjustments and expenses in the accompanying Consolidated Statement of Operations. The Company determines the fair value of earnouts (contingent consideration) and any subsequent changes in fair value using a discounted probability-weighted approach using Level 3 inputs. Level 3 valuations rely on unobservable inputs for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. The fair value of the earnouts is reviewed quarterly and is based on the payments the Company expects to make based on historical internal observations related to the anticipated performance of the underlying assets. The Company’s estimate of the fair value of its obligation contained in acquisitions prior to January 1, 2017 (adoption of ASU 2017-01) was $0.5 million and $2.5 million as of December 31, 2018 and 2017, respectively. The maximum potential obligation related to the performance targets for these acquisitions was $0.7 million and $3.1 million as of December 31, 2018 and 2017, respectively. The maximum potential obligation related to the performance targets for acquisitions after January 1, 2017, which have not been recorded on the Company’s Consolidated Balance Sheet, were $13.3 million and $11.1 million as of December 31, 2018 and 2017.

The Company’s asset retirement obligations are measured at fair value on a recurring basis using Level 3 inputs and are recorded in Other long-term liabilities in the accompanying Consolidated Balance Sheets. The fair value of the asset retirement obligations is calculated using a discounted cash flow model.

Items Measured at Fair Value on a Nonrecurring Basis— The Company’s long-lived and intangible assets are measured at fair value on a nonrecurring basis using Level 3 inputs. The Company considers many factors and makes certain assumptions when making this assessment, including but not limited to: general market and economic conditions, historical operating results, geographic location, lease-up potential and expected timing of lease-up. The fair value of the long-lived and intangible assets is calculated using a discounted cash flow model.

Asset impairment and decommission costs for all periods presented and the related impaired assets primarily relate to the Company’s site leasing operating segment. The following summarizes the activity of asset impairment and decommission costs (in thousands):



	For the year
	ended December 31,
	2018		2017		2016

Asset impairment (1)	$	14,350	$	15,389	$	19,217
Write-off of carrying value of decommissioned towers		10,795		16,861		12,967
Gain on sale of fiber assets (2)		—		—		(8,919)
Other (including third party decommission costs)		1,989		4,447		6,977
Total asset impairment and decommission costs	$	27,134	$	36,697	$	30,242

(1)Represents impairment charges resulting from the Company’s regular analysis of whether the future cash flows from certain towers are adequate to recover the carrying value of the investment in those towers.

(2)Gain recognized on the sale of fiber assets acquired in the 2012 Mobilitie transaction.

Fair Value of Financial Instruments— The carrying values of cash and cash equivalents, accounts receivable, restricted cash, accounts payable, and short-term investments approximate their estimated fair values due to the short maturity of these instruments. Short-term investments consisted of $0.2 million in Treasury securities as of December 31, 2018 and 2017. The Company’s estimate of the fair value of its held-to-maturity investments in treasury and corporate bonds, including current portion, are based primarily upon Level 1 reported market values. As of December 31, 2018, the carrying value and fair value of the held-to-maturity investments, including current portion, were $0.2 million. As of December 31, 2017, the carrying value and fair value of the held-to-maturity investments, including current portion, were $0.5 million. The current portion is recorded in Prepaid and other current assets in the accompanying Consolidated Balance Sheets, while held-to-maturity investments are recorded in Other assets. For the year ended December 31, 2018, the Company purchased $150.0 million and sold $150.2 million of short-term investments.

The Company determines fair value of its debt instruments utilizing various Level 2 sources including quoted prices and indicative quotes (non-binding quotes) from brokers that require judgment to interpret market information including implied credit spreads for similar borrowings on recent trades or bid/ask prices. The fair value of the Revolving Credit Facility is considered to approximate the carrying value because the interest payments are based on Eurodollar rates that reset monthly or more frequently. The Company does not believe its credit risk has changed materially from the date the applicable Eurodollar Rate was set for the Revolving Credit Facility (112.5 to 175.0 basis points). Refer to Note 12 for the fair values, principal balances, and carrying values of the Company’s debt instruments.

- Definition

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

+ References + Details

Restricted Cash

12 Months Ended

Dec. 31, 2018

Restricted Cash [Abstract]

Restricted Cash

4.RESTRICTED CASH

The cash, cash equivalents, and restricted cash balances on the consolidated statement of cash flows consists of the following:



	As of		As of		As of
	December 31, 2018		December 31, 2017		December 31, 2016		Included on Balance Sheet

		(in thousands)
Cash and cash equivalents	$	143,444	$	68,783	$	146,109
Securitization escrow accounts		32,261		32,699		36,607	Restr. cash - current asset
Payment and performance bonds		203		225		179	Restr. cash - current asset
Surety bonds and workers compensation		2,392		2,588		3,075	Other assets - noncurrent
Total cash, cash equivalents, and restr. cash	$	178,300	$	104,295	$	185,970

Pursuant to the terms of the Tower Securities (see Note 12), the Company is required to establish a securitization escrow account, held by the indenture trustee, into which all rents and other sums due on the towers that secure the Tower Securities are directly deposited by the lessees. These restricted cash amounts are used to fund reserve accounts for the payment of (1) debt service costs, (2) ground rents, real estate and personal property taxes and insurance premiums related to towers, (3) trustee and servicing expenses, and (4) management fees. The restricted cash in the securitization escrow account in excess of required reserve balances is subsequently released to the Borrowers (as defined in Note 12) monthly, provided that the Borrowers are in compliance with their debt service coverage ratio and that no event of default has occurred. All monies held by the indenture trustee are classified as restricted cash on the Company’s Consolidated Balance Sheets.

Payment and performance bonds relate primarily to collateral requirements for tower construction currently in process by the Company. Cash is pledged as collateral related to surety bonds issued for the benefit of the Company or its affiliates in the ordinary course of business and primarily related to the Company’s tower removal obligations. As of December 31, 2018 and 2017, the Company had $40.5 million and $39.5 million in surety, payment and performance bonds, respectively, for which no collateral was required to be posted. The Company periodically evaluates the collateral posted for its bonds to ensure that it meets the minimum requirements. As of December 31, 2018 and 2017, the Company had also pledged $2.2 and $2.5 million, respectively, as collateral related to its workers compensation policy.

Prepaid Expenses and Other Current Assets and Other Assets

12 Months Ended

Dec. 31, 2018

Prepaid Expenses and Other Current Assets and Other Assets [Abstract]

Prepaid Expenses and Other Current Assets and Other Assets

5.PREPAID EXPENSES AND OTHER CURRENT ASSETS AND OTHER ASSETS

The Company’s prepaid expenses and other current assets are comprised of the following:



	As of		As of
	December 31, 2018		December 31, 2017

		(in thousands)
Prepaid ground rent	$	34,276	$	32,505
Loan receivables		11,178		948
Other		17,672		16,263
Total prepaid expenses and other current assets	$	63,126	$	49,716

The Company’s other assets are comprised of the following:



	As of		As of
	December 31, 2018		December 31, 2017

		(in thousands)
Prepaid ground rent	$	263,694	$	220,493
Straight-line rent receivable		322,073		313,650
Loan receivables		49,255		52,383
Deferred lease costs, net		27,020		27,703
Deferred tax asset - long term		18,330		1,670
Other		41,661		34,296
Total other assets	$	722,033	$	650,195

Acquisitions

12 Months Ended

Dec. 31, 2018

Acquisitions [Abstract]

Acquisitions

6.ACQUISITIONS

The following table summarizes the Company’s acquisition activity:



	For the year ended December 31,
	2018		2017		2016
Tower acquisitions (number of towers)		1,316		1,425		531

The following table summarizes the Company’s cash acquisition capital expenditures:



	For the year ended December 31,
	2018		2017		2016

		(in thousands)
Acquisitions of towers and related intangible assets (1)	$	406,699	$	392,902	$	214,686
Land buyouts and other assets (2)		45,130		48,645		62,149
Total cash acquisition capital expenditures	$	451,829	$	441,547	$	276,835

(1)

The year ended December 31, 2017 excludes $63.3 million of acquisition costs funded through the issuance of 487,963 shares of Class A common stock.

(2)

In addition, the Company paid $24.3 million, $18.8 million, and $14.1 million for ground lease extensions and term easements on land underlying the Company’s towers during the years ending December 31, 2018, 2017, and 2016, respectively. The Company recorded these amounts in prepaid rent on its Consolidated Balance Sheets.

During the year ended December 31, 2018, the Company acquired 1,316 completed towers and related assets and liabilities consisting of $134.5 million of property and equipment, $280.7 million of intangible assets, and $8.5 million of working capital adjustments.

During the year ended December 31, 2017, the Company acquired 1,425 completed towers and related assets and liabilities consisting of $114.7 million of property and equipment, $345.3 million of intangible assets, and $3.8 million of working capital adjustments.

During the year ended December 31, 2016, the Company acquired 531 completed towers and related assets and liabilities for $214.7 million in cash consisting of $72.8 million of property and equipment, $144.4 million of intangible assets, and $2.5 million of working capital adjustments.

Subsequent to December 31, 2018, the Company acquired 27 towers and related assets for $10.7 million in cash.

Intangible Assets, Net

12 Months Ended

Dec. 31, 2018

Intangible Assets, Net [Abstract]

Intangible Assets, Net

7.INTANGIBLE ASSETS, NET

The following table provides the gross and net carrying amounts for each major class of intangible assets:



	As of December 31, 2018						As of December 31, 2017
	Gross carrying		Accumulated		Net book		Gross carrying		Accumulated		Net book
	amount		amortization		value		amount		amortization		value

	(in thousands)
Current contract intangibles	$	4,394,416	$	(1,928,030)	$	2,466,386	$	4,355,171	$	(1,673,270)	$	2,681,901
Network location intangibles		1,669,859		(804,780)		865,079		1,617,441		(701,211)		916,230
Intangible assets, net	$	6,064,275	$	(2,732,810)	$	3,331,465	$	5,972,612	$	(2,374,481)	$	3,598,131

All intangible assets noted above are included in the Company’s site leasing segment. The Company amortizes its intangible assets using the straight-line method over 15 years. Amortization expense relating to the intangible assets above was $402.6 million, $384.1 million, and $369.9 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Estimated amortization expense on the Company’s intangibles assets is as follows:



For the year ended December 31,	(in thousands)

2019	$	403,371
2020		402,447
2021		369,864
2022		349,657
2023		327,181

Property and Equipment, Net

12 Months Ended

Dec. 31, 2018

Property and Equipment, Net [Abstract]

Property and Equipment, Net

8.PROPERTY AND EQUIPMENT, NET

Property and equipment, net (including vehicles held under capital leases) consists of the following:



	As of		As of
	December 31, 2018		December 31, 2017

	(in thousands)
Towers and related components	$	4,951,321	$	4,772,807
Construction-in-process		35,756		34,689
Furniture, equipment, and vehicles		54,814		53,260
Land, buildings, and improvements		668,459		630,370
Total property and equipment		5,710,350		5,491,126
Less: accumulated depreciation		(2,923,995)		(2,678,780)
Property and equipment, net	$	2,786,355	$	2,812,346

Construction-in-process represents costs incurred related to towers that are under development and will be used in the Company’s site leasing operations. Depreciation expense was $269.2 million, $258.4 million, and $268.1 million for the years ended December 31, 2018, 2017, and 2016, respectively. At December 31, 2018 and 2017, non-cash capital expenditures that are included in accounts payable and accrued expenses were $12.4 million.

Costs and Estimated Earnings on Uncompleted Contracts

12 Months Ended

Dec. 31, 2018

Costs and Estimated Earnings on Uncompleted Contracts [Abstract]

Costs and Estimated Earnings on Uncompleted Contracts

9.COSTS AND ESTIMATED EARNINGS ON UNCOMPLETED CONTRACTS

The Company’s costs and estimated earnings on uncompleted contracts are comprised of the following:



	As of		As of
	December 31, 2018		December 31, 2017

	(in thousands)
Costs incurred on uncompleted contracts	$	38,464	$	31,404
Estimated earnings		16,655		10,541
Billings to date		(31,952)		(24,771)
	$	23,167	$	17,174

These amounts are included in the accompanying Consolidated Balance Sheets under the following captions:



	As of		As of
	December 31, 2018		December 31, 2017

	(in thousands)
Costs and estimated earnings in excess of billings on uncompleted contracts	$	23,785	$	17,437
Billings in excess of costs and estimated earnings on
uncompleted contracts (included in Other current liabilities)		(618)		(263)
	$	23,167	$	17,174

At December 31, 2018 and 2017, eight customers comprised 96.3% and 87.9%, respectively, of the costs and estimated earnings in excess of billings on uncompleted contracts, net of billings in excess of costs and estimated earnings, respectively.

Concentration of Credit Risk

12 Months Ended

Dec. 31, 2018

Concentration of Credit Risk [Abstract]

Concentration of Credit Risk

10.CONCENTRATION OF CREDIT RISK

The Company’s credit risks consist primarily of accounts receivable with national, regional, and local wireless service providers and federal and state government agencies. The Company performs periodic credit evaluations of its customers’ financial condition and provides allowances for doubtful accounts, as required, based upon factors surrounding the credit risk of specific customers, historical trends, and other information. The Company generally does not require collateral.

The following is a list of significant customers (representing at least 10% of revenue for any period reported) and the percentage of total revenue for the specified time periods derived from such customers:



	For the year ended December 31,
Percentage of Total Revenues	2018	2017	2016

AT&T Wireless	24.0%	25.0%	25.7%
Sprint	17.9%	15.1%	16.1%
T-Mobile	16.4%	16.5%	17.0%
Verizon Wireless	14.7%	15.2%	15.2%

The Company’s site leasing and site development segments derive revenue from these customers. Client percentages of total revenue in each of the segments are as follows:



	For the year ended December 31,
Percentage of Domestic Site Leasing Revenue	2018	2017	2016

AT&T Wireless	31.9%	32.7%	32.7%
T-Mobile	20.3%	19.7%	19.6%
Sprint	19.6%	18.9%	19.8%
Verizon Wireless	19.0%	19.0%	18.2%

	For the year ended December 31,
Percentage of International Site Leasing Revenue	2018	2017	2016

Oi S.A.	35.5%	42.2%	43.9%
Telefonica	26.7%	25.7%	26.4%
Claro	11.4%	10.0%	9.4%



	For the year ended December 31,
Percentage of Site Development Revenue	2018	2017	2016

Sprint	47.1%	12.9%	11.7%
T-Mobile	16.4%	26.9%	28.4%
Verizon Wireless	6.4%	12.8%	16.5%
Nokia, Inc.	3.2%	10.1%	7.1%

Five customers comprised 67.5% of total gross accounts receivable at December 31, 2018 compared to five customers which comprised 66.9% of total gross accounts receivable at December 31, 2017.

Earnings Per Share

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Earnings Per Share

11.EARNINGS PER SHARE

Basic earnings per share was computed by dividing net income attributable to common shareholders by the weighted-average number of shares of Common Stock outstanding for each respective period. Diluted earnings per share was calculated by dividing net income attributable to common shareholders by the weighted-average number of shares of Common Stock outstanding adjusted for any dilutive Common Stock equivalents, including unvested restricted stock and shares issuable upon exercise of stock options as determined under the “If-Converted” method and also Common Stock warrants as determined under the “Treasury Stock” method.

The following table sets forth basic and diluted net income per common share for the years ended December 31, 2018, 2017, and 2016 (in thousands, except per share data):



	For the year ended December 31,
	2018		2017		2016
Numerator:
Net income	$	47,451	$	103,654	$	76,238
Denominator:
Basic weighted-average shares outstanding		114,909		119,860		124,448
Dilutive impact of stock options and restricted shares		1,606		1,162		696
Diluted weighted-average shares outstanding		116,515		121,022		125,144
Net income per common share:
Basic	$	0.41	$	0.86	$	0.61
Diluted	$	0.41	$	0.86	$	0.61

For the year ended December 31, 2018, the diluted weighted average number of common shares outstanding excluded an additional 0.8 million shares issuable upon exercise of the Company’s stock options because the impact would be anti-dilutive.

For the year ended December 31, 2017, the diluted weighted average number of common shares outstanding excluded an additional 1.0 million shares issuable upon exercise of the Company’s stock options because the impact would be anti-dilutive.

For the year ended December 31, 2016, the diluted weighted average number of common shares outstanding excluded an additional 2.2 million shares issuable upon exercise of the Company’s stock options because the impact would be anti-dilutive.

Debt

12 Months Ended

Dec. 31, 2018

Debt [Abstract]

Debt

12. DEBT

The principal values, fair values, and carrying values of debt consist of the following (in thousands):



		As of						As of
		December 31, 2018						December 31, 2017
	Maturity Date	Principal Balance		Fair Value		Carrying Value		Principal Balance		Fair Value		Carrying Value
2014 Senior Notes	Jul. 15, 2022	$	750,000	$	735,000	$	741,273	$	750,000	$	770,625	$	739,079
2016 Senior Notes	Sep. 1, 2024		1,100,000		1,034,000		1,083,689		1,100,000		1,127,500		1,081,262
2017 Senior Notes	Oct. 1, 2022		750,000		712,500		743,099		750,000		750,938		741,437
2013-1C Tower Securities	Apr. 10, 2018		—		—		—		425,000		423,853		424,482
2013-2C Tower Securities	Apr. 11, 2023		575,000		569,164		569,715		575,000		578,433		568,609
2013-1D Tower Securities	Apr. 10, 2018		—		—		—		330,000		330,145		329,585
2014-1C Tower Securities	Oct. 8, 2019		920,000		914,241		917,728		920,000		915,216		914,929
2014-2C Tower Securities	Oct. 8, 2024		620,000		609,665		614,315		620,000		620,942		613,461
2015-1C Tower Securities	Oct. 8, 2020		500,000		496,640		495,737		500,000		496,840		493,474
2016-1C Tower Securities	Jul. 9, 2021		700,000		691,432		694,994		700,000		691,166		693,118
2017-1C Tower Securities	Apr. 11, 2022		760,000		744,496		753,028		760,000		751,404		751,076
2018-1C Tower Securities	Mar. 9, 2023		640,000		641,478		632,725		—		—		—
Revolving Credit Facility	Apr. 11, 2023		325,000		325,000		325,000		40,000		40,000		40,000
2014 Term Loan	Mar. 24, 2021		—		—		—		1,447,500		1,451,119		1,439,373
2015 Term Loan	Jun. 10, 2022		—		—		—		487,500		488,109		480,801
2018 Term Loan	Apr. 11, 2025		2,388,000		2,262,630		2,367,250		—		—		—
Total debt		$	10,028,000	$	9,736,246	$	9,938,553	$	9,405,000	$	9,436,290	$	9,310,686
Less: current maturities of long-term debt							(941,728)						(20,000)
Total long-term debt, net of current maturities						$	8,996,825					$	9,290,686

The Company’s future principal payment obligations over the next five years (based on the outstanding debt as of December 31, 2018 and assuming the Tower Securities are repaid at their respective anticipated repayment dates) are as follows:



For the year ended December 31,	(in thousands)
2019	$	944,000
2020		524,000
2021		724,000
2022		2,284,000
2023		1,564,000

The table below reflects cash and non-cash interest expense amounts recognized by debt instrument for the periods presented:



	For the year ended December 31,
	2018				2017				2016
	Cash		Non-cash		Cash		Non-cash		Cash		Non-cash
	Interest		Interest		Interest		Interest		Interest		Interest

	(in thousands)
5.625% Senior Notes		—		—		—		—		21,094		—
5.75% Senior Notes		—		—		—		—		28,494		—
2014 Senior Notes		36,563		761		36,563		724		36,563		689
2016 Senior Notes		53,625		1,003		53,625		954		20,258		348
2017 Senior Notes		30,000		—		6,500		—		—		—
2010-2C Tower Securities		—		—		—		—		15,213		—
2012 Tower Securities		—		—		5,330		—		18,107		—
2013 Tower Securities		25,654		—		43,217		—		43,217		—
2014 Tower Securities		51,138		—		51,138		—		51,138		—
2015-1C Tower Securities		15,939		—		15,939		—		15,939		—
2016-1C Tower Securities		20,361		—		20,361		—		9,898		—
2017-1C Tower Securities		24,354		—		17,182		—		—		—
2018-1C Tower Securities		18,072		—		—		—		—		—
Revolving Credit Facility		7,411		—		8,046		—		4,167		—
2014 Term Loan		15,550		146		49,414		525		48,962		510
2015 Term Loan		5,237		187		16,641		676		16,487		656
2018 Term Loan		72,648		543		—		—		—		—
Capitalized interest and other		(335)		—		(207)		—		(366)		—
Total	$	376,217	$	2,640	$	323,749	$	2,879	$	329,171	$	2,203

Senior Credit Agreement

On April 11, 2018, the Company amended and restated its Senior Credit Agreement to (1) issue a new $2.4 billion Term Loan, (2) increase the total commitments under the Revolving Credit Facility from $1.0 billion to $1.25 billion, (3) extend the maturity date of the Revolving Credit Facility to April 11, 2023, (4) lower the applicable interest rate margins and commitment fees under the Revolving Credit Facility, and (5) amend certain other terms and conditions under the Senior Credit Agreement. The proceeds from the new Term Loan were used to repay the outstanding balances on the 2014 Term Loan, 2015 Term Loan, and Revolving Credit Facility and for general corporate purposes. This transaction was accounted for as an extinguishment of the 2014 Term Loan and 2015 Term Loan.

Terms of the Senior Credit Agreement

The Senior Credit Agreement, as amended, requires SBA Senior Finance II to maintain specific financial ratios, including (1) a ratio of Consolidated Net Debt to Annualized Borrower EBITDA not to exceed 6.5 times for any fiscal quarter, (2) a ratio of Consolidated Net Debt (calculated in accordance with the Senior Credit Agreement) to Annualized Borrower EBITDA for the most recently ended fiscal quarter not to exceed 6.5 times for 30 consecutive days and (3) a ratio of Annualized Borrower EBITDA to Annualized Cash Interest Expense (calculated in accordance with the Senior Credit Agreement) of not less than 2.0 times for any fiscal quarter. The Senior Credit Agreement contains customary affirmative and negative covenants that, among other things, limit the ability of SBA Senior Finance II and its subsidiaries to incur indebtedness, grant certain liens, make certain investments, enter into sale leaseback transactions, merge or consolidate, make certain restricted payments, enter into transactions with affiliates, and engage in certain asset dispositions, including a sale of all or substantially all of their property. The Senior Credit Agreement is also subject to customary events of default. Pursuant to the Second Amended and Restated Guarantee and Collateral Agreement, amounts borrowed under the Revolving Credit Facility, the Term Loans and certain hedging transactions that may be entered into by SBA Senior Finance II or the Subsidiary Guarantors (as defined in the Senior Credit Agreement) with lenders or their affiliates are secured by a first lien on the membership interests of SBA Telecommunications, LLC, SBA Senior Finance, LLC and SBA Senior Finance II and on substantially all of the assets (other than leasehold, easement and fee interests in real property) of SBA Senior Finance II and the Subsidiary Guarantors.

The Senior Credit Agreement, as amended, permits SBA Senior Finance II, without the consent of the other lenders, to request that one or more lenders provide SBA Senior Finance II with increases in the Revolving Credit Facility or additional term loans provided that after giving effect to the proposed increase in Revolving Credit Facility commitments or incremental term loans the ratio of Consolidated Net Debt to Annualized Borrower EBITDA would not exceed 6.5 times. SBA Senior Finance II’s ability to request such increases in the Revolving Credit Facility or additional term loans is subject to its compliance with customary conditions set forth in the Senior Credit Agreement including compliance, on a pro forma basis, with the financial covenants and ratios set forth therein and, with respect to any additional term loan, an increase in the margin on existing term loans to the extent required by the terms of the Senior Credit Agreement. Upon SBA Senior Finance II’s request, each lender may decide, in its sole discretion, whether to increase all or a portion of its Revolving Credit Facility commitment or whether to provide SBA Senior Finance II with additional term loans and, if so, upon what terms.

Revolving Credit Facility under the Senior Credit Agreement

As amended, the Revolving Credit Facility consists of a revolving loan under which up to $1.25 billion aggregate principal amount may be borrowed, repaid and redrawn, based upon specific financial ratios and subject to the satisfaction of other customary conditions to borrowing. Amounts borrowed under the Revolving Credit Facility accrue interest, at SBA Senior Finance II’s election, at either (1) the Eurodollar Rate plus a margin that ranges from 112.5 basis points to 175.0 basis points or (2) the Base Rate plus a margin that ranges from 12.5 basis points to 75.0 basis points, in each case based on the ratio of Consolidated Net Debt to Annualized Borrower EBITDA, calculated in accordance with the Senior Credit Agreement. In addition, SBA Senior Finance II is required to pay a commitment fee of between 0.20% and 0.25% per annum on the amount of unused commitment. If not earlier terminated by SBA Senior Finance II, the Revolving Credit Facility will terminate on, and SBA Senior Finance II will repay all amounts outstanding on or before, April 11, 2023. The proceeds available under the Revolving Credit Facility may be used for general corporate purposes. SBA Senior Finance II may, from time to time, borrow from and repay the Revolving Credit Facility. Consequently, the amount outstanding under the Revolving Credit Facility at the end of the period may not be reflective of the total amounts outstanding during such period.

During the year ended December 31, 2018, the Company borrowed $1.1 billion and repaid $835.0 million of the outstanding balance under the Revolving Credit Facility. As of December 31, 2018, the balance outstanding under the Revolving Credit Facility was $325.0 million accruing interest at 4.38% per annum. In addition, SBA Senior Finance II was required to pay a commitment fee of 0.25% per annum on the amount of the unused commitment. As of December 31, 2018, SBA Senior Finance II was in compliance with the financial covenants contained in the Senior Credit Agreement.

Subsequent to December 31, 2018, the Company repaid $120.0 million of the outstanding balance under the Revolving Credit Facility. As of the date of this filing, $205.0 million was outstanding under the Revolving Credit Facility.

Term Loans under the Senior Credit Agreement

2014 Term Loan

The 2014 Term Loan consisted of a senior secured term loan with an initial aggregate principal amount of $1.5 billion that was scheduled to mature on March 24, 2021. The 2014 Term Loan accrued interest, at SBA Senior Finance II’s election, at either the Base Rate plus 125 basis points (with zero Base Rate floor) or the Eurodollar Rate plus 225 basis points (with a zero Eurodollar Rate floor). The 2014 Term Loan was originally issued at 99.75% of par value. Principal payments on the 2014 Term Loan commenced on September 30, 2014 and were being made in quarterly installments on the last day of each March, June, September, and December in an amount equal to $3.8 million. The Company incurred deferred financing fees of approximately $14.1 million in relation to this transaction which were being amortized through the maturity date.

During the three months ended March 31, 2018, the Company repaid $3.8 million of principal on the 2014 Term Loan. On April 11, 2018, the Company repaid the remaining $1,443.8 million outstanding principal balance of the 2014 Term Loan with proceeds from the 2018 Term Loan. In connection with the repayment, the Company expensed $5.8 million of net deferred financing fees and $1.7 million of discount related to the debt.

2015 Term Loan

The 2015 Term Loan consisted of a senior secured term loan with an initial aggregate principal amount of $500.0 million that was scheduled to mature on June 10, 2022. The 2015 Term Loan accrued interest, at SBA Senior Finance II’s election at either the Base Rate plus 125 basis points (with a zero Base Rate floor) or the Eurodollar Rate plus 225 basis points (with a zero Eurodollar Rate floor). The 2015 Term Loan was originally issued at 99.0% of par value. Principal payments on the 2015 Term Loan commenced on September 30, 2015 and were being made in quarterly installments on the last day of each March, June, September, and December in an amount equal to $1.3 million. The Company incurred financing fees of approximately $5.5 million in relation to this transaction, which were being amortized through the maturity date.

During the three months ended March 31, 2018, the Company repaid $1.3 million of principal on the 2015 Term Loan. On April 11, 2018, the Company repaid the remaining $486.3 million outstanding principal balance of the 2015 Term Loan with proceeds from the 2018 Term Loan. In connection with the repayment, the Company expensed $3.2 million of net deferred financing fees and $3.1 million of discount related to the debt.

2018 Term Loan

On April 11, 2018, the Company, through its wholly owned subsidiary, SBA Senior Finance II LLC, obtained a new term loan (the “2018 Term Loan”) under the amended and restated Senior Credit Agreement. The 2018 Term Loan consists of a senior secured term loan with an initial aggregate principal amount of $2.4 billion that matures on April 11, 2025. The 2018 Term Loan accrues interest, at SBA Senior Finance II’s election at either the Base Rate plus 100 basis points (with a zero Base Rate floor) or the Eurodollar Rate plus 200 basis points (with a zero Eurodollar Rate floor). The 2018 Term Loan was issued at 99.75% of par value. As of December 31, 2018, the 2018 Term Loan was accruing interest at 4.53% per annum. Principal payments on the 2018 Term Loan commenced on September 30, 2018 and are being made in quarterly installments on the last day of each March, June, September, and December in an amount equal to $6.0 million. The Company incurred financing fees of approximately $16.8 million in relation to this transaction, which are being amortized through the maturity date. The proceeds from the 2018 Term Loan were used (1) to retire the outstanding $1.93 billion in aggregate principal amount of the 2014 Term Loan and 2015 Term Loan, (2) to pay down the existing outstanding balance under the Revolving Credit Facility, and (3) for general corporate purposes.

During the year ended December 31, 2018, the Company repaid an aggregate of $12.0 million of principal on the 2018 Term Loan. As of December 31, 2018, the 2018 Term Loan had a principal balance of $2.4 billion.

On February 1, 2019, the Company, through its wholly owned subsidiary, SBA Senior Finance II, LLC, entered into a four-year interest rate swap on a portion of its 2018 Term Loan. The Company swapped $1.2 billion of notional value accruing interest at one month LIBOR plus 200 basis points for a fixed rate of 4.495% per annum.

Secured Tower Revenue Securities

Tower Revenue Securities Terms

The mortgage loan underlying the 2013-2C Tower Securities, 2014 Tower Securities, 2015-1C Tower Securities, 2016-1C Tower Securities, 2017-1C Tower Securities, and 2018-1C Tower Securities (together the “Tower Securities”) will be paid from the operating cash flows from the aggregate 10,426 tower sites owned by the Borrowers. The sole asset of the Trust consists of a non-recourse mortgage loan made in favor of those entities that are borrowers on the mortgage loan (the “Borrowers”). The mortgage loan is secured by (1) mortgages, deeds of trust, and deeds to secure debt on a substantial portion of the tower sites, (2) a security interest in the tower sites and substantially all of the Borrowers’ personal property and fixtures, (3) the Borrowers’ rights under certain tenant leases, and (4) all of the proceeds of the foregoing. For each calendar month, SBA Network Management, Inc., an indirect subsidiary (“Network Management”), is entitled to receive a management fee equal to 4.5% of the Borrowers’ operating revenues for the immediately preceding calendar month.

The Borrowers may prepay any of the mortgage loan components, in whole or in part, with no prepayment consideration, (1) within twelve months (in the case of the component corresponding to the Secured Tower Revenue Securities Series 2014-1C, Secured Tower Revenue Securities Series 2015-1C, Secured Tower Revenue Securities Series 2016-1C, Secured Tower Revenue Securities Series 2017-1C, and Secured Tower Revenue Securities Series 2018-1C) or eighteen months (in the case of the components corresponding to the Secured Tower Revenue Securities Series 2013-2C and Secured Tower Revenue Securities Series 2014-2C) of the anticipated repayment date of such mortgage loan component, (2) with proceeds received as a result of any condemnation or casualty of any tower owned by the Borrowers or (3) during an amortization period. In all other circumstances, the Borrowers may prepay the mortgage loan, in whole or in part, upon payment of the applicable prepayment consideration. The prepayment consideration is determined based on the class of the Tower Securities to which the prepaid mortgage loan component corresponds and consists of an amount equal to the excess, if any, of (1) the present value associated with the portion of the principal balance being prepaid, calculated in accordance with the formula set forth in the mortgage loan agreement, on the date of prepayment of all future installments of principal and interest required to be paid from the date of prepayment to and including the first due date within twelve months (in the case of the component corresponding to the Secured Tower Revenue Securities Series 2014-1C, Secured Tower Revenue Securities Series 2015-1C, Secured Tower Revenue Securities Series 2016-1C, Secured Tower Revenue Securities Series 2017-1C, and Secured Tower Revenue Securities Series 2018-1C) or eighteen months (in the case of the components corresponding to the Secured Tower Revenue Securities Series 2013-2C and Secured Tower Revenue Securities Series 2014-2C) of the anticipated repayment date of such mortgage loan component over (2) that portion of the principal balance of such class prepaid on the date of such prepayment.

To the extent that the mortgage loan components corresponding to the Tower Securities are not fully repaid by their respective anticipated repayment dates, the interest rate of each such component will increase by the greater of (1) 5% and (2) the amount, if any, by which the sum of (x) the ten-year U.S. treasury rate plus (y) the credit-based spread for such component (as set forth in the mortgage loan agreement) plus (z) 5%, exceeds the original interest rate for such component.

Pursuant to the terms of the Tower Securities, all rents and other sums due on any of the towers owned by the Borrowers are directly deposited by the lessees into a controlled deposit account and are held by the indenture trustee. The monies held by the indenture trustee after the release date are classified as short-term restricted cash on the Consolidated Balance Sheets (see Note 4). However, if the Debt Service Coverage Ratio, defined as the net cash flow (as defined in the mortgage loan agreement) divided by the amount of interest on the mortgage loan, servicing fees and trustee fees that the Borrowers are required to pay over the succeeding twelve months, as of the end of any calendar quarter, falls to 1.30x or lower, then all cash flow in excess of amounts required to make debt service payments, to fund required reserves, to pay management fees and budgeted operating expenses and to make other payments required under the loan documents, referred to as “excess cash flow,” will be deposited into a reserve account instead of being released to the Borrowers. The funds in the reserve account will not be released to the Borrowers unless the Debt Service Coverage Ratio exceeds 1.30x for two consecutive calendar quarters. If the Debt Service Coverage Ratio falls below 1.15x as of the end of any calendar quarter, then an “amortization period” will commence and all funds on deposit in the reserve account will be applied to prepay the mortgage loan until such time that the Debt Service Coverage Ratio exceeds 1.15x for a calendar quarter. In addition, if any of the Tower Securities are not fully repaid by their respective anticipated repayment dates, the cash flow from the towers owned by the Borrowers will be trapped by the trustee for the Tower Securities and applied first to repay the interest, at the original interest rates, on the mortgage loan components underlying the Tower Securities, second to fund all reserve accounts and operating expenses associated with those towers, third to pay the management fees due to Network Management, fourth to repay principal of the Tower Securities and fifth to repay the additional interest discussed above. Furthermore, the advance rents reserve requirement states that the Borrowers are required to maintain an advance rents reserve at any time the monthly tenant Debt Service Coverage Ratio is equal to or less than 2:1 and for two calendar months after such coverage ratio again exceeds 2:1. The mortgage loan agreement, as amended, also includes covenants customary for mortgage loans subject to rated securitizations. Among other things, the Borrowers are prohibited from incurring other indebtedness for borrowed money or further encumbering their assets.

2010-2C Tower Securities

On April 16, 2010, the Company, through a New York common law trust (the “Trust”), issued $550.0 million of 2010-2C Tower Securities (the “2010-2C Tower Securities”). The 2010-2C Tower Securities had an annual interest rate of 5.101%. The anticipated repayment date and the final maturity date for the 2010–2C Tower Securities were April 11, 2017 and April 9, 2042, respectively. The Company incurred deferred financing fees of $8.1 million in relation to this transaction which were being amortized through the anticipated repayment date of the 2010-2C Tower Securities.

On July 15, 2016, the Company repaid in full the 2010-2C Tower Securities with proceeds from the 2016-1C Tower Securities. Additionally, the Company expensed $1.0 million of deferred financing fees related to the redemption of the 2010-2C Tower Securities, which are reflected in loss from extinguishment of debt on the Consolidated Statement of Operations.

2012-1C Tower Securities

On August 9, 2012, the Company, through the Trust, issued $610.0 million of Secured Tower Revenue Securities Series 2012-1C (the “2012-1C Tower Securities”), which had an anticipated repayment date of December 11, 2017 and a final maturity date of December 9, 2042. The fixed interest rate of the 2012-1C Tower Securities was 2.933% per annum, payable monthly. The Company incurred deferred financing fees of $14.9 million in relation to this transaction, which were being amortized through the anticipated repayment date of the 2012-1C Tower Securities.

On April 17, 2017, the Company repaid in full the 2012-1C Tower Securities with proceeds from the 2017-1C Tower Securities. In connection with the repayment, the Company expensed $2.0 million of net deferred financing fees.

2013 Tower Securities

On April 18, 2013, the Company, through the Trust, issued $425.0 million of 2.240% Secured Tower Revenue Securities Series 2013-1C, which had an anticipated repayment date of April 10, 2018 and a final maturity date of April 9, 2043 (the “2013-1C Tower Securities”), $575.0 million of 3.722% Secured Tower Revenue Securities Series 2013-2C, which have an anticipated repayment date of April 11, 2023 and a final maturity date of April 9, 2048 (the “2013-2C Tower Securities”), and $330.0 million of 3.598% Secured Tower Revenue Securities Series 2013-1D, which had an anticipated repayment date of April 10, 2018 and a final maturity date of April 9, 2043 (the “2013-1D Tower Securities”) (collectively the “2013 Tower Securities”). The aggregate $1.33 billion of 2013 Tower Securities had a blended interest rate of 3.218% per annum, payable monthly. The Company incurred financing fees of $25.5 million in relation to this transaction, which were being amortized through the anticipated repayment date of each of the 2013 Tower Securities.

On March 9, 2018, the Company repaid the entire aggregate principal amount of the 2013-1C Tower Securities and 2013-1D Tower Securities in connection with the issuance of the 2018-1C Tower Securities (as defined below).

The sole asset of the Trust consists of a non-recourse mortgage loan made in favor of those entities that are borrowers on the mortgage loan (the “Borrowers”).

2014 Tower Securities

On October 15, 2014, the Company, through the Trust, issued $920.0 million of 2.898% Secured Tower Revenue Securities Series 2014-1C, which have an anticipated repayment date of October 8, 2019 and a final maturity date of October 11, 2044 (the “2014-1C Tower Securities”) and $620.0 million of 3.869% Secured Tower Revenue Securities Series 2014-2C, which have an anticipated repayment date of October 8, 2024 and a final maturity date of October 8, 2049 (the “2014-2C Tower Securities”) (collectively the “2014 Tower Securities”). The aggregate $1.54 billion of 2014 Tower Securities have a blended interest rate of 3.289% per annum, payable monthly. The Company incurred financing fees of $22.5 million in relation to this transaction, which are being amortized through the anticipated repayment date of each of the 2014 Tower Securities.

2015-1C Tower Securities

On October 14, 2015, the Company, through the Trust, issued $500.0 million of Secured Tower Revenue Securities Series 2015-1C, which have an anticipated repayment date of October 8, 2020 and a final maturity date of October 10, 2045 (the “2015-1C Tower Securities”). The fixed interest rate of the 2015-1C Tower Securities is 3.156% per annum, payable monthly. The Company incurred financing fees of $11.2 million in relation to this transaction, which are being amortized through the anticipated repayment date of the 2015-1C Tower Securities.

2016-1C Tower Securities

On July 7, 2016, the Company, through the Trust, issued $700.0 million of Secured Tower Revenue Securities Series 2016-1C, which have an anticipated repayment date of July 9, 2021 and a final maturity date of July 10, 2046 (the “2016-1C Tower Securities”). The fixed interest rate of the 2016-1C Tower Securities is 2.877% per annum, payable monthly. The Company incurred financing fees of $9.5 million in relation to this transaction, which are being amortized through the anticipated repayment date of the 2016-1C Tower Securities.

2017-1C Tower Securities

On April 17, 2017, the Company, through the Trust, issued $760.0 million of Secured Tower Revenue Securities Series 2017-1C, which have an anticipated repayment date of April 11, 2022 and a final maturity date of April 9, 2047 (the “2017-1C Tower Securities”). The fixed interest rate on the 2017-1C Tower Securities is 3.168% per annum, payable monthly. Net proceeds from this offering were used to prepay the entire $610.0 million aggregate principal amount, as well as accrued and unpaid interest, of the 2012-1C Tower Securities and for general corporate purposes. The Company incurred financing fees of $10.2 million in relation to this transaction, which are being amortized through the anticipated repayment date of the 2017-1C Tower Securities.

In addition, to satisfy certain risk retention requirements of Regulation RR promulgated under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), SBA Guarantor, LLC, a wholly owned subsidiary, purchased $40.0 million of Secured Tower Revenue Securities Series 2017-1R issued by the Trust, which have an anticipated repayment date of April 11, 2022 and a final maturity date of April 9, 2047 (the “2017-1R Tower Securities”). The fixed interest rate on the 2017-1R Tower Securities is 4.459% per annum, payable monthly. Principal and interest payments made on the 2017-1R Tower Securities eliminate in consolidation.

2018-1C Tower Securities

On March 9, 2018, the Company, through the Trust, issued $640.0 million of Secured Tower Revenue Securities Series 2018-1C, which have an anticipated repayment date of March 9, 2023 and a final maturity date of March 9, 2048 (the “2018-1C Tower Securities”). The fixed interest rate on the 2018-1C Tower Securities is 3.448% per annum, payable monthly. Net proceeds from this offering, in combination with borrowings under the Revolving Credit Facility, were used to repay the entire aggregate principal amount of the 2013-1C Tower Securities ($425.0 million) and 2013-1D Tower Securities ($330.0 million), as well as accrued and unpaid interest. The Company incurred financing fees of $8.5 million in relation to this transaction, which are being amortized through the anticipated repayment date of the 2018-1C Tower Securities.

In addition, to satisfy certain risk retention requirements of Regulation RR promulgated under the Exchange Act, SBA Guarantor, LLC, a wholly owned subsidiary, purchased $33.7 million of Secured Tower Revenue Securities Series 2018-1R issued by the Trust. These securities have an anticipated repayment date of March 9, 2023 and a final maturity date of March 9, 2048 (the “2018-1R Tower Securities”). The fixed interest rate on the 2018-1R Tower Securities is 4.949% per annum, payable monthly. Principal and interest payments made on the 2018-1R Tower Securities eliminate in consolidation.

In connection with the issuance of the 2018-1C Tower Securities, the non-recourse mortgage loan was increased by $673.7 million (but decreased by a net of $81.3 million after giving effect to prepayment of the loan components relating to the 2013-1C Tower Securities and 2013-1D Tower Securities). The new loan, after eliminating the risk retention securities, accrues interest at the same rate as the 2018-1C Tower Securities and is subject to all other material terms of the existing mortgage loan, including collateral and interest rate after the anticipated repayment date.

In connection with the issuance of the 2018-1C Tower Securities, SBA Properties, LLC, SBA Sites, LLC, SBA Structures, LLC, SBA Infrastructure, LLC, SBA Monarch Towers III, LLC, SBA 2012 TC Assets PR, LLC, SBA 2012 TC Assets, LLC, SBA Towers IV, LLC, SBA Monarch Towers I, LLC, SBA Towers USVI, Inc., SBA Towers VII, LLC, SBA GC Towers, LLC, SBA Towers V, LLC, and SBA Towers VI, LLC (collectively, the “Borrowers”), each an indirect subsidiary of SBAC, and Midland Loan Services, a division of PNC Bank, National Association, as servicer, on behalf of the Trustee entered into the Second Loan and Security Agreement Supplement and Amendment pursuant to which, among other things, (1) the outstanding principal amount of the mortgage loan was increased by $640.0 million and (2) the Borrowers became jointly and severally liable for the aggregate $4.7 billion borrowed under the mortgage loan corresponding to the 2013-2C Tower Securities, 2014 Tower Securities, 2015-1C Tower Securities, 2016-1C Tower Securities, 2017-1C Tower Securities, and the newly issued 2018-1C Tower Securities.

Debt Covenants

As of December 31, 2018, the Borrowers met the debt service coverage ratio required by the mortgage loan agreement and were in compliance with all other covenants as set forth in the agreement.

Senior Notes

5.75% Senior Notes

On July 13, 2012, Telecommunications issued $800.0 million of unsecured senior notes due July 15, 2020 (the “5.75% Senior Notes”). The 5.75% Senior Notes accrued interest at a rate of 5.75% and were issued at par. The Company incurred financing fees of $14.0 million in relation to this transaction, which were being amortized through the maturity date.

On August 15, 2016, the Company used proceeds from the 2016 Senior Notes to redeem the full $800.0 million in aggregate principal amount of the 5.75% Senior Notes and to pay $25.8 million for the call premium and accrued interest on the redemption of the notes. Additionally, the Company expensed $7.7 million of deferred financing fees related to the redemption of the notes. The call premium and the write-off of deferred financing fees are reflected in loss from extinguishment of debt on the Consolidated Statement of Operations.

SBAC is a holding company with no business operations of its own and its only significant asset is the outstanding capital stock of Telecommunications. Telecommunications is 100% owned by SBAC. SBAC had fully and unconditionally guaranteed the Senior Notes issued by Telecommunications.

5.625% Senior Notes

On September 28, 2012, the Company issued $500.0 million of unsecured senior notes due October 1, 2019 (the “5.625% Senior Notes”). The 5.625% Senior Notes accrued interest at a rate of 5.625% per annum and were issued at par. Interest on the 5.625% Senior Notes was due semi-annually on April 1 and October 1 of each year. The Company incurred financing fees of $8.6 million in relation to this transaction, which were being amortized through the maturity date.

On October 1, 2016, the Company redeemed the 5.625% Senior Notes in full. On October 3, 2016, the Company repaid $500.0 million in outstanding principal, $14.1 million related to the call premium on the early redemption of the notes, and $14.1 million in accrued interest. Repayment was made using (1) the proceeds from the 2016 Senior Notes, (2) borrowings under the Revolving Credit Facility, and (3) cash on hand. In addition, the Company expensed $4.1 million of deferred financing fees related to the redemption of the notes. The call premium and the write-off of deferred financing fees are reflected in loss from extinguishment of debt on the Consolidated Statement of Operations.

2014 Senior Notes

On July 1, 2014, the Company issued $750.0 million of unsecured senior notes due July 15, 2022 (the “2014 Senior Notes”). The 2014 Senior Notes accrue interest at a rate of 4.875% per annum and were issued at 99.178% of par value. Interest on the 2014 Senior Notes is due semi-annually on January 15 and July 15 of each year. The Company incurred financing fees of $11.6 million in relation to this transaction, which are being amortized through the maturity date.

The 2014 Senior Notes are subject to redemption in whole or in part at the redemption prices set forth in the indenture agreement plus accrued and unpaid interest. The Company may redeem the 2014 Senior Notes during the twelve-month period beginning on the following dates at the following redemption prices: July 15, 2019 at 101.219% or July 15, 2020 until maturity at 100.000% of the principal amount of the 2014 Senior Notes to be redeemed on the redemption date plus accrued and unpaid interest.

2016 Senior Notes

On August 15, 2016, the Company issued $1.1 billion of unsecured senior notes due September 1, 2024 (the “2016 Senior Notes”). The 2016 Senior Notes accrue interest at a rate of 4.875% per annum and were issued at 99.178% of par value. Interest on the 2016 Senior Notes is due semi-annually on March 1 and September 1 of each year, beginning on March 1, 2017. The Company incurred financing fees of $12.8 million in relation to this transaction, which are being amortized through the maturity date. Net proceeds from this offering and cash on hand were used to redeem $800.0 million, the aggregate principal amount outstanding, of Telecommunications’ 5.75% Senior Notes and $250.0 million of the Company’s 5.625% Senior Notes and pay the associated call premiums.

The 2016 Senior Notes are subject to redemption in whole or in part on or after September 1, 2019 at the redemption prices set forth in the indenture agreement plus accrued and unpaid interest. Prior to September 1, 2019, the Company may at its option redeem up to 35% of the aggregate principal amount of the 2016 Senior Notes originally issued at a redemption price of 104.875% of the principal amount of the 2016 Senior Notes to be redeemed on the redemption date plus accrued and unpaid interest with the net proceeds of certain equity offerings. The Company may redeem the 2016 Senior Notes during the twelve-month period beginning on the following dates at the following redemption prices: September 1, 2019 at 103.656%, September 1, 2020 at 102.438%, September 1, 2021 at 101.219%, or September 1, 2022 until maturity at 100.000%, of the principal amount of the 2016 Senior Notes to be redeemed on the redemption date plus accrued and unpaid interest.

2017 Senior Notes

On October 13, 2017, the Company issued $750.0 million of unsecured senior notes due October 1, 2022 (the “2017 Senior Notes”). The 2017 Senior Notes accrue interest at a rate of 4.0% per annum. Interest on the 2017 Senior Notes is due semi-annually on April 1 and October 1 of each year, beginning on April 1, 2018. The Company incurred financing fees of $8.9 million in relation to this transaction, which are being amortized through the maturity date. Net proceeds from this offering were used to repay $460.0 million outstanding under the Revolving Credit Facility and for general corporate purposes.

The 2017 Senior Notes are subject to redemption in whole or in part on or after October 1, 2019 at the redemption prices set forth in the indenture agreement plus accrued and unpaid interest. Prior to October 1, 2020, the Company may, at its option, redeem up to 35% of the aggregate principal amount of the 2017 Senior Notes originally issued at a redemption price of 104.000% of the principal amount of the 2017 Senior Notes to be redeemed on the redemption date plus accrued and unpaid interest with the net proceeds of certain equity offerings. The Company may redeem the 2017 Senior Notes during the twelve-month period beginning on the following dates at the following redemption prices: October 1, 2019 at 102.000%, October 1, 2020 at 101.000%, or October 1, 2021 until maturity at 100.000%, of the principal amount of the 2017 Senior Notes to be redeemed on the redemption date plus accrued and unpaid interest.

Indentures Governing Senior Notes

The Indentures governing the Senior Notes contain customary covenants, subject to a number of exceptions and qualifications, including restrictions on the ability of SBAC and Telecommunications to (1) incur additional indebtedness unless the Consolidated Indebtedness to Annualized Consolidated Adjusted EBITDA Ratio (as defined in the Indenture), pro forma for the additional indebtedness does not exceed, with respect to any fiscal quarter, 9.5x for SBAC, (2) merge, consolidate or sell assets, (3) make restricted payments, including dividends or other distributions, (4) enter into transactions with affiliates, and (5) enter into sale and leaseback transactions and restrictions on the ability of the Restricted Subsidiaries of SBAC (as defined in the Indentures) to incur liens securing indebtedness.

Shareholders' Equity	12 Months Ended
Shareholders' Equity	Dec. 31, 2018
Shareholders' Equity [Abstract]
Shareholders' Equity	13.SHAREHOLDERS’ EQUITY Common Stock Equivalents The Company has potential common stock equivalents (see Note 14) related to its outstanding stock options and restricted stock units These potential common stock equivalents were considered in the Company’s diluted earnings per share calculation (see Note 11). Stock Repurchases On June 4, 2015, the Company’s Board of Directors authorized a $1.0 billion stock repurchase plan, replacing the plan authorized on April 27, 2011. This plan authorized the Company to purchase, from time to time, up to $1.0 billion of the outstanding Class A common stock through open market repurchases in compliance with Rule 10b-18 under the Exchange Act, and/or in privately negotiated transactions at management’s discretion based on market and business conditions, applicable legal requirements, and other factors. During the year ended December 31, 2016, the Company repurchased 5.3 million shares of its Class A common stock under this stock repurchase program for $545.7 million at a weighted average price per share of $102.14. During the year ended December 31, 2017, the Company repurchased 42,163 shares of its Class A common stock under this stock repurchase plan for $4.4 million at a weighted average price per share of $104.81. Shares repurchased were retired. On January 12, 2017, the Company’s Board of Directors authorized a $1.0 billion stock repurchase plan, replacing the plan authorized on June 4, 2015. This plan authorized the Company to purchase, from time to time, up to $1.0 billion of the Company’s outstanding Class A common stock through open market repurchases in compliance with Rule 10b-18 under the Exchange Act, and/or in privately negotiated transactions at management’s discretion based on market and business conditions, applicable legal requirements, and other factors. During the year ended December 31, 2017, the Company repurchased 5.8 million shares of its Class A common stock under this plan for $850.0 million, at an average price per share of $146.17. Shares repurchased were retired. On February 16, 2018, the Company’s Board of Directors authorized a $1.0 billion stock repurchase plan, replacing the plan authorized on January 12, 2017. This plan authorizes the Company to purchase, from time to time, up to $1.0 billion of the outstanding Class A common stock through open market repurchases in compliance with Rule 10b-18 under the Exchange Act, and/or in privately negotiated transactions at management’s discretion based on market and business conditions, applicable legal requirements, and other factors. This plan has no time deadline and will continue until otherwise modified or terminated by the Company’s Board of Directors at any time in its sole discretion. During the year ended December 31, 2018, the Company repurchased 5.0 million shares of its Class A common stock under this plan for $795.5 million, at an average price per share of $159.87. Shares repurchased were retired. As of the date of this filing, the Company had $204.5 million authorization remaining under this plan. Registration of Additional Shares On May 20, 2010, the Company filed a registration statement on Form S-8 with the Securities and Exchange Commission registering 15.0 million shares of the Company’s Class A common stock issuable under the 2010 Performance and Equity Incentive Plan (see Note 14). The Company filed a shelf registration statement on Form S-4 with the Securities and Exchange Commission registering 4.0 million shares of its Class A common stock in 2007. These shares may be issued in connection with acquisitions of wireless communication towers or antenna sites and related assets or companies that own wireless communication towers, antenna sites, or related assets. During the year ended December 31, 2018 and 2016, the Company did not issue any shares of its Class A common stock pursuant to this registration statement in connection with acquisitions. During the year ended December 31, 2017, the Company issued 487,963 shares of Class A common stock under this registration statement. As of December 31, 2018, the Company had approximately 1.2 million shares of Class A common stock remaining under this registration statement. On March 5, 2018, the Company filed with the Commission an automatic shelf registration statement for well-known seasoned issuers on Form S-3ASR. This registration statement enables the Company to issue shares of its Class A common stock, preferred stock or debt securities either separately or represented by warrants, or depositary shares as well as units that include any of these securities. Under the rules governing automatic shelf registration statements, the Company will file a prospectus supplement and advise the Commission of the amount and type of securities each time it issues securities under this registration statement. For the year ended December 31, 2018, the Company did not issue any securities under this automatic shelf registration statement.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2018

Stock-Based Compensation [Abstract]

Stock-Based Compensation

14.STOCK-BASED COMPENSATION

The Company has an equity participation plan (the 2010 Performance and Equity Incentive Plan, the “2010 Plan”) whereby options (both non-qualified and incentive stock options), restricted stock units, stock appreciation rights, and other equity and performance based instruments may be granted to directors, employees, and consultants. The options and restricted stock units generally vest from the date of grant on a straight-line basis over the vesting term and generally have a seven-year or a ten-year contractual life.

The 2010 Plan was adopted by the Company’s shareholders on May 6, 2010 and provides for the issuance of a maximum of 15.0 million shares of the Company’s Class A common stock, of which 6.5 million shares remain available for future issuance as of December 31, 2018. However, the aggregate number of shares that may be issued pursuant to restricted stock awards, restricted stock unit awards, stock bonus awards, performance awards, other stock-based awards, or other awards granted under the 2010 Plan will not exceed 7.5 million shares, of which 6.5 million shares remain available for future issuance as of December 31, 2018.

During 2018, the Board of Directors adopted a retirement policy applicable to all employees receiving equity as part of their compensation plan. This policy is effective January 1, 2019. Historically, all unvested equity awards granted would be forfeited the day after an employee stops working for the Company and any options that were vested but unexercised would be forfeited 90 days after the employee stopped working. The new retirement policy allows employees that meet certain conditions to retire and keep unvested equity awards and extends the time the employee has to exercise vested and outstanding awards. As a result of this policy, stock compensation expense related to the adoption of the policy will result in an acceleration of unrecognized stock compensation expense of approximately $11.2 million and $7.3 million in the first and second quarter of 2019, respectively.

Stock Options

The Company records compensation expense for employee stock options based on the estimated fair value of the options on the date of grant using the Black-Scholes option-pricing model with the assumptions included in the table below. The Company uses a combination of historical data and historical volatility to establish the expected volatility, as well as to estimate the expected option life. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for the estimated life of the option. The following assumptions were used to estimate the fair value of options granted using the Black-Scholes option-pricing model:



	For the year ended December 31,
	2018	2017	2016

Risk free interest rate	2.57% - 2.92%	1.70% - 1.97%	1.11% - 1.43%
Dividend yield	0.7%	0.0%	0.0%
Expected volatility	21.6%	20.0%	20.0%
Expected lives	4.6 years	4.6 years	4.7 years

The following table summarizes the Company’s activities with respect to its stock option plans for the years ended December 31, 2018, 2017 and 2016 as follows (dollars and shares in thousands, except for per share data):



		Weighted-		Weighted-Average
		Average		Remaining
	Number	Exercise Price		Contractual	Aggregate
	of Shares	Per Share		Life (in years)	Intrinsic Value
Outstanding at December 31, 2015	3,794	$	84.66
Granted	1,357	$	96.64
Exercised	(603)	$	46.03
Forfeited/canceled	(101)	$	105.37
Outstanding at December 31, 2016	4,447	$	93.09
Granted	1,171	$	115.41
Exercised	(709)	$	80.73
Forfeited/canceled	(67)	$	105.81
Outstanding at December 31, 2017	4,842	$	100.12
Granted	941	$	156.55
Exercised	(926)	$	81.73
Forfeited/canceled	(41)	$	123.98
Outstanding at December 31, 2018	4,816	$	114.48	4.2	$	228,248
Exercisable at December 31, 2018	2,162	$	100.15	3.0	$	133,490
Unvested at December 31, 2018	2,654	$	126.17	5.1	$	94,758

The weighted-average per share fair value of options granted during the years ended December 31, 2018, 2017 and 2016 was $33.01, $23.88, and $19.19, respectively.

The total intrinsic value for options exercised during the years ended December 31, 2018, 2017 and 2016 was $78.0 million, $37.2 million and $36.8 million, respectively. Cash received from option exercises under all plans for the years ended December 31, 2018, 2017 and 2016 was approximately $74.7 million, $56.5 million, and $27.4 million, respectively. No tax benefit was realized for the tax deductions from option exercises under all plans for the years ended December 31, 2018, 2017 and 2016, respectively.

The aggregate intrinsic value for stock options in the preceding table represents the total intrinsic value based on the Company’s closing stock price of $161.89 as of December 31, 2018. The amount represents the total intrinsic value that would have been received by the holders of the stock-based awards had these awards been exercised and sold as of that date.

Additional information regarding options outstanding and exercisable at December 31, 2018 is as follows:



	Options Outstanding				Options Exercisable
		Weighted Average	Weighted			Weighted
		Remaining	Average			Average
Range	Outstanding	Contractual Life	Exercise Price		Exercisable	Exercise Price
	(in thousands)	(in years)			(in thousands)
$0.00 - $90.00	406	1.0	$	68.96	406	$	68.96
$90.01 - $110.00	1,609	3.5	$	96.29	983	$	96.08
$110.01 - $145.00	1,871	4.4	$	119.15	773	$	121.69
$145.01 - $175.00	930	6.2	$	156.55	—	$	0.00
	4,816				2,162

The following table summarizes the activity of options outstanding that had not yet vested:



		Weighted-
		Average
	Number	Fair Value
	of Shares	Per Share
	(in thousands)
Unvested as of December 31, 2017	2,860	$	22.08
Shares granted	941	$	33.01
Vesting during period	(1,104)	$	21.74
Forfeited/canceled	(43)	$	26.32
Unvested as of December 31, 2018	2,654	$	26.05

As of December 31, 2018, the total unrecognized compensation expense related to unvested stock options outstanding under the Plans is $43.3 million. That cost is expected to be recognized over a weighted average period of 2.5 years.

The total fair value of options vested during 2018, 2017, and 2016 was $24.0 million, $21.4 million, and $18.5 million, respectively.

Restricted Stock Units

The following table summarizes the Company’s restricted stock unit activity for the year ended December 31, 2018:



		Weighted-Average
	Number of	Grant Date Fair
	Shares	Value per Share
	(in thousands)
Outstanding at December 31, 2017	328	$	110.20
Granted	138	$	156.61
Vested	(129)	$	110.93
Forfeited/canceled	(13)	$	135.22
Outstanding at December 31, 2018	324	$	128.69

As of December 31, 2018, total unrecognized compensation expense related to unvested restricted stock units granted under the 2010 Plan was $28.1 million and is expected to be recognized over a weighted-average period of 2.6 years.

Employee Stock Purchase Plan

In 2008, the Board of Directors of the Company adopted the 2008 Employee Stock Purchase Plan (“2008 Purchase Plan”) which reserved 500,000 shares of Class A common stock for purchase. The 2008 Purchase Plan permits eligible employee participants to purchase Class A common stock at a price per share which is equal to 85% of the fair market value of Class A common stock on the last day of an offering period.

For the year ended December 31, 2018, 16,798 shares of Class A common stock were issued under the 2008 Purchase Plan, which resulted in cash proceeds to the Company of approximately $2.3 million, compared to the year ended December 31, 2017 when 28,232 shares of Class A common stock were issued under the 2008 Purchase Plan which resulted in cash proceeds to the Company of $3.3 million.

On May 23, 2018, the Board of Directors of the Company adopted the 2018 Employee Stock Purchase Plan (“2018 Purchase Plan”) which replaced the 2008 Purchase Plan and reserved 300,000 shares of Class A common stock for purchase. The 2018 Purchase Plan permits eligible employee participants to purchase Class A common stock at a price per share which is equal to 85% of the fair market value of Class A common stock on the last day of an offering period.

For the year ended December 31, 2018, 10,052 shares of Class A common stock were issued under the 2018 Purchase Plan, which resulted in cash proceeds to the Company of approximately $1.4 million. At December 31, 2018, 289,948 shares remained available for issuance under the 2018 Purchase Plan.

In addition, the Company recorded $0.6 million, $0.6 million, and $0.5 million of non-cash compensation expense relating to the shares issued under the 2008 Purchase Plan and 2018 Purchase Plan for each of the years ended December 31, 2018, 2017, and 2016, respectively.

Non-Cash Compensation Expense

The table below reflects a break out by category of the non-cash compensation expense amounts recognized on the Company’s Statements of Operations for the years ended December 31, 2018, 2017, and 2016, respectively:



		For the year ended December 31,
	2018		2017		2016
	(in thousands)
Cost of revenues	$	1,182	$	1,013	$	418
Selling, general and administrative		41,145		37,236		32,497
Total cost of non-cash compensation included
in loss before provision for income taxes		42,327		38,249		32,915
Amount of income tax recognized in earnings		—		—		—
Amount charged against loss	$	42,327	$	38,249	$	32,915

In addition, the Company capitalized $0.8 million, $0.6 million and $0.5 million of non-cash compensation for the years ended December 31, 2018, 2017 and 2016, respectively, to fixed assets.

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Taxes [Abstract]

Income Taxes

15. INCOME TAXES

As discussed in Note 2, the Company began operating in compliance with REIT requirements for federal income tax purposes effective January 1, 2016. As a REIT, the Company must distribute at least 90 percent of its taxable income (including dividends paid to it by its TRSs) except to the extent offset by NOLs. In addition, the Company must meet a number of other organizational and operational requirements. It is management's intention to adhere to these requirements and maintain the Company's REIT status. Most states where SBA operates conform to the federal rules recognizing REITs. Certain subsidiaries have made an election with the Company to be treated as TRSs in conjunction with the Company's REIT election; the TRS elections permit SBA to engage in certain business activities in which the REIT may not engage directly. A TRS is subject to federal and state income taxes on the income from these activities. A provision for taxes of the TRSs and of foreign branches of the REIT is included in its consolidated financial statements.

Income before provision for income taxes by geographic area is as follows:



		For the year ended December 31,
	2018		2017		2016

	(in thousands)
Domestic	$	99,203	$	73,405	$	(28,671)
Foreign		(47,519)		43,486		115,974
Total	$	51,684	$	116,891	$	87,303

The provision for income taxes consists of the following components:



		For the year ended December 31,
	2018		2017		2016

	(in thousands)
Current provision:
State	$	5,764	$	5,513	$	1,535
Foreign		13,756		11,681		8,121
Total current		19,520		17,194		9,656

Deferred provision (benefit) for taxes:
Federal		(9,463)		18,736		170,177
State		(1,412)		(241)		22,992
Foreign		(16,673)		9,155		30,425
Change in valuation allowance		12,261		(31,607)		(222,185)
Total deferred		(15,287)		(3,957)		1,409
Total provision for income taxes	$	4,233	$	13,237	$	11,065

A reconciliation of the provision for income taxes at the statutory U.S. Federal tax rate (21% for 2018 and 35% for 2017 and 2016) and the effective income tax rate is as follows:



	For the year ended December 31,
	2018		2017		2016

	(in thousands)
Statutory federal expense	$	10,854	$	40,912	$	30,555
Rate and permanent differences on non-U.S. earnings (1)		3,620		3,690		(4,739)
State and local tax expense		4,824		5,415		3,941
REIT adjustment		(22,241)		(34,346)		205,317
Permanent differences		437		(1,365)		(3,577)
Tax Act impact on deferred taxes		(6,040)		31,547		—
Other		518		(1,009)		1,753
Valuation allowance		12,261		(31,607)		(222,185)
Provision for income taxes	$	4,233	$	13,237	$	11,065

(1)

This item includes the effect of foreign exchange rate changes which were previously shown on a separate line.

The components of the net deferred income tax asset (liability) accounts are as follows:



	As of December 31,
	2018			2017

	(in thousands)
Noncurrent deferred tax assets:
Net operating losses	$	63,622	$	65,257
Property, equipment, and intangible basis differences		4,793		3,038
Accrued liabilities		9,659		11,933
Non-cash compensation		16,641		7,500
Deferred revenue		2,005		2,110
Allowance for doubtful accounts		5,691		5,978
Currency translation		56,604		34,895
Other		2,480		2,698
Valuation allowance		(50,628)		(38,802)
Total noncurrent deferred tax assets, net (1)		110,867		94,607

Noncurrent deferred tax liabilities:
Property, equipment, and intangible basis differences		(114,652)		(98,589)
Straight-line rents		(20,469)		(22,740)
Deferred foreign withholding taxes		(6,225)		—
Deferred lease costs		(2,192)		(2,242)
Other		(123)		(136)
Total noncurrent deferred tax liabilities, net (1)	$	(32,794)	$	(29,100)

(1)Of these amounts, $18,330 and $51,124 are included in Other assets and Other long-term liabilities, respectively on the accompanying Consolidated Balance Sheets as of December 31, 2018. As of December 31, 2017, $1,670 and $30,770 are included in Other assets and Other long-term liabilities on the accompanying Consolidated Balance Sheet.

A deferred tax asset is reduced by a valuation allowance if based on the weight of all available evidence, including both positive and negative evidence, it is more likely than not (a likelihood of more than 50%) that the value of such assets will not be realized. The valuation allowance should be sufficient to reduce the deferred tax asset to the amount that is more likely than not to be realized. The realization of deferred tax assets, including carryforwards and deductible temporary differences, depends upon the existence of sufficient taxable income of the same character during the carryback or carryforward period. All sources of taxable income available to realize the deferred tax asset, including the future reversal of existing temporary differences, future taxable income exclusive of reversing temporary differences and carryforwards, taxable income in carryback years and tax-planning strategies, should be considered.

The Company has recorded a valuation allowance for certain deferred tax assets as management believes that it is not “more-likely-than-not” that the Company will generate sufficient taxable income in future periods to recognize the assets. Valuation allowances of $50.6 million and $38.8 million were being carried to offset net deferred income tax assets as of December 31, 2018 and 2017, respectively. The net change in the valuation allowance for the years ended December 31, 2018 and 2017 was a decrease of $11.8 million and an increase of $31.4 million, respectively. During 2018, the Company released the valuation allowance on the majority of its deferred tax assets related to its Brazil operations as it was determined that it is “more-likely-than-not” the Brazil operations will generate sufficient taxable income to recognize the assets.

The Company has available at December 31, 2018, a federal NOL carry-forward of approximately $863.1 million. $857.5 million of these NOL carry-forwards will expire between 2024 and 2037, and $5.6 million have an indefinite carry-forward. As of December 31, 2018, $755.4 million of the federal NOLs are attributes of the REIT. The Company may use these NOLs to offset its REIT taxable income, and thus any required distributions to shareholders may be reduced or eliminated until such time as the NOLs have been fully utilized. The Internal Revenue Code places limitations upon the future availability of NOLs based upon changes in the equity of the Company. If these occur, the ability of the Company to offset future income with existing NOLs may be limited. In addition, the Company has available at December 31, 2018, a foreign NOL carry-forward of $85.0 million and a net state operating tax loss carry-forward of approximately $412.2 million. These net operating tax loss carry-forwards begin to expire in 2020.

The U.S. tax losses generated in tax years 2001 through 2013 remain subject to adjustment, and tax years 2015 through 2018 are open to examination by the major jurisdictions in which the Company operates.

The Company has removed the permanent reinvestment assertion as of December 31, 2018 for all foreign earnings of our foreign jurisdictions except for Argentina. The Company recorded deferred foreign withholding taxes of $6.2 million at December 31, 2018 for this change in the Company’s permanent reinvestment assertion and will accrue additional withholding taxes as foreign earnings are generated. No additional income taxes have been provided for any additional outside basis difference inherent in these entities, as these amounts continue to be indefinitely reinvested in foreign operations. Determining the amount of unrecognized deferred tax liability for any additional outside basis differences in these entities is not practicable.

On December 22, 2017, the U.S. government enacted comprehensive tax legislation in the form of the Tax Cuts and Jobs Act (the “Tax Act”) that significantly revised the U.S. tax code effective January 1, 2018 by, among other things, lowering the corporate income tax rate from a top marginal rate of 35% to a flat 21%, imposing a mandatory one-time deemed repatriation of foreign earnings (commonly referred to as the “transition tax”), creating new taxes on certain foreign-sourced income, and limiting deductibility of interest expense and certain executive compensation. The Company applied the guidance in SAB 118 when accounting for the enactment-date effects of the Tax Act in 2017 and throughout 2018. At December 31, 2017, the Company made a reasonable estimate of the one-time transition tax on accumulated foreign earnings as well as the impact of the Tax Act on its existing deferred tax balances. During the fourth quarter of 2018, the Company completed its accounting for all of the enactment-date income tax effects of the Tax Act.

The one-time transition tax is based on the Company’s total post-1986 earnings and profits (“E&P”), which was previously deferred from U.S. income taxes. The Company recorded $52.4 million as a provisional amount of the one-time transition taxable income at December 31, 2017. During 2018, the Company finalized its calculations of the post-1986 E&P as well as the cash balances of the foreign subsidiaries whose earnings were subject to the transition tax. Following the completion of this analysis, the Company reduced its transition taxable income to $49.2 million. Subsequent to the Company’s year-end, the Treasury Department finalized regulations for the calculation of the transition tax, and the Company is analyzing the impact of these regulations on its calculation. The Company has elected to include the transition taxable income inclusion over the eight-year period provided in the Tax Act. As of December 31, 2018, the remaining balance of the Company’s transition tax inclusion amount is $41.3 million, which will be included in taxable income over the next six years.

As of December 31, 2017, the Company recorded a reduction to its deferred tax asset and offsetting valuation allowance in the amount of $12.3 million related to new limitations on the deductibility of executive compensation in the Tax Act. Upon further analysis of the Tax Act during 2018, the Company determined that $6.0 million of the deferred tax asset should be recorded, which amount is offset by a valuation allowance. The Company will elect qualifying real property trade or business status for the REIT, and is thus not subject to the interest limitation provisions of the Tax Act.

The Tax Act subjects a U.S. shareholder to tax on Global Intangible Low-Taxed Income (“GILTI”) earned by certain foreign subsidiaries. The FASB Staff Q&A, Topic 740, No. 5, Accounting for Global Intangible Low-Taxed Income, states that an entity can make an accounting policy election to either recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years or to provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only. The Company has elected to account for GILTI in the year it is incurred. The income inclusion for GILTI for 2018 is $10.2 million.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies [Abstract]

Commitments and Contingencies

16.COMMITMENTS AND CONTINGENCIES

Leases

The Company is obligated under various non-cancelable operating leases for land, office space, equipment and site leases that expire at various times through December 2152. In addition, the Company is obligated under various non-cancelable capital leases for vehicles that expire at various times through August 2022.

The annual minimum lease payments under non-cancelable operating (primarily ground or land leases) and capital leases for the next five years as of December 31, 2018 are as follows (in thousands):



For the year ended December 31,	Capital Leases		Operating Leases
2019	$	883	$	237,730
2020		482		239,208
2021		303		241,090
2022		86		242,320
2023		—		243,476
Total minimum lease payments		1,754
Less: amount representing interest		(83)
Present value of future payments		1,671
Less: current obligations		(860)
Long-term obligations	$	811

Future minimum rental payments under noncancelable ground leases include payments for certain renewal periods at the Company’s option because failure to renew could result in a loss of the applicable tower and related revenue from tenant leases, thereby making it reasonably assured that the Company will renew the lease. The majority of operating leases provide for renewal at varying escalations. Fixed rate escalations have been included in the table disclosed above.

Rent expense for operating leases was $273.5 million, $266.4 million and $253.7 million for the years ended December 31, 2018, 2017 and 2016, respectively. In addition, certain of the Company’s leases include contingent rent provisions which provide for the lessor to receive additional rent upon the attainment of certain tower operating results and/or lease-up. Contingent rent expense for the years ended December 31, 2018, 2017 and 2016 was $27.1 million, $26.6 million and $25.0 million, respectively.

Tenant Leases

The annual minimum tower lease income to be received for tower space and antenna rental under non-cancelable operating leases for the next five years as of December 31, 2018 is as follows:



For the year ended December 31,	(in thousands)
2019	$	1,529,902
2020		1,326,108
2021		1,075,675
2022		815,219
2023		598,987

The Company’s tenant leases provide for annual escalations and multiple renewal periods, at the tenant’s option. The tenant rental payments disclosed in the table above do not assume exercise of any tenant renewal options, however, fixed rate escalations have been included for the current term.

Litigation

The Company is involved in various claims, lawsuits and proceedings arising in the ordinary course of business. While there are uncertainties inherent in the ultimate outcome of such matters and it is impossible to presently determine the ultimate costs that may be incurred, management believes the resolution of such uncertainties and the incurrence of such costs will not have a material adverse effect on the Company’s consolidated financial position, results of operations or liquidity.

Contingent Purchase Obligations

From time to time, the Company agrees to pay additional consideration (or earnouts) for acquisitions if the towers or businesses that are acquired meet or exceed certain performance targets in the one to three years after they have been acquired. Please refer to Note 3.

Defined Contribution Plan	12 Months Ended
Defined Contribution Plan	Dec. 31, 2018
Defined Contribution Plan [Abstract]
Defined Contribution Plan	17.DEFINED CONTRIBUTION PLAN The Company has a defined contribution profit sharing plan under Section 401(k) of the Internal Revenue Code that provides for voluntary employee contributions up to the limitations set forth in Section 402(g) of the Internal Revenue Code. Employees have the opportunity to participate following completion of three months of employment and must be 21 years of age. Employer matching begins immediately upon the employee’s participation in the plan. The Company makes a discretionary matching contribution of 75% of an employee’s contributions up to a maximum of $4,000 annually. Company matching contributions were approximately $2.1 million, $2.0 million and $2.0 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Segment Data

12 Months Ended

Dec. 31, 2018

Segment Data [Abstract]

Segment Data

18.SEGMENT DATA

The Company operates principally in two business segments: site leasing and site development. The Company’s site leasing business includes two reportable segments, domestic site leasing and international site leasing. The Company’s business segments are strategic business units that offer different services. They are managed separately based on the fundamental differences in their operations. The site leasing segment includes results of the managed and sublease businesses. The site development segment includes the results of both consulting and construction related activities. The Company’s Chief Operating Decision Maker utilizes segment operating profit and operating income as his two measures of segment profit in assessing performance and allocating resources at the reportable segment level. The Company has applied the aggregation criteria to operations within the international site leasing segment on a basis that is consistent with management’s review of information and performance evaluations of the individual markets in this region.

Revenues, cost of revenues (exclusive of depreciation, accretion and amortization), capital expenditures (including assets acquired through the issuance of shares of the Company’s Class A common stock) and identifiable assets pertaining to the segments in which the Company continues to operate are presented below.



	Domestic Site		Int'l Site		Site		Not Identified
	Leasing		Leasing		Development		by Segment		Total

For the year ended December 31, 2018	(in thousands)
Revenues	$	1,400,095	$	340,339	$	125,261	$	—	$	1,865,695
Cost of revenues (2)		266,131		106,165		96,499		—		468,795
Operating profit		1,133,964		234,174		28,762		—		1,396,900
Selling, general, and administrative		72,879		27,082		16,215		26,350		142,526
Acquisition related adjustments and expenses		5,268		5,693		—		—		10,961
Asset impairment and decommission costs		18,857		7,932		345		—		27,134
Depreciation, amortization and accretion		511,823		151,570		2,556		6,164		672,113
Operating income (loss)		525,137		41,897		9,646		(32,514)		544,166
Other expense (principally interest expense
and other expense)								(492,482)		(492,482)
Income before provision for income taxes										51,684
Cash capital expenditures (3)		338,610		258,785		1,561		3,724		602,680
For the year ended December 31, 2017
Revenues	$	1,308,389	$	314,784	$	104,501	$	—	$	1,727,674
Cost of revenues (2)		260,826		98,701		86,785		—		446,312
Operating profit		1,047,563		216,083		17,716		—		1,281,362
Selling, general, and administrative		67,263		24,320		15,433		23,681		130,697
Acquisition related adjustments and expenses		8,171		4,196		—		—		12,367
Asset impairment and decommission costs		29,523		6,994		180		—		36,697
Depreciation, amortization and accretion		498,842		135,155		2,580		6,523		643,100
Operating income (loss)		443,764		45,418		(477)		(30,204)		458,501
Other expense (principally interest expense
and other expense)								(341,610)		(341,610)
Income before provision for income taxes										116,891
Cash capital expenditures (3)		225,074		358,691		1,221		3,859		588,845
For the year ended December 31, 2016
Revenues	$	1,273,866	$	264,204	$	95,055	$	—	$	1,633,125
Cost of revenues (2)		260,941		81,274		78,682		—		420,897
Operating profit		1,012,925		182,930		16,373		—		1,212,228
Selling, general, and administrative (4)		72,701		35,897		13,039		21,712		143,349
Acquisition related adjustments and expenses		6,233		6,907		—		—		13,140
Asset impairment and decommission costs		26,073		1,824		—		2,345		30,242
Depreciation, amortization and accretion		509,108		119,466		3,402		6,213		638,189
Operating income (loss)		398,810		18,836		(68)		(30,270)		387,308
Other expense (principally interest expense
and other expense)								(300,005)		(300,005)
Income before provision for income taxes										87,303
Cash capital expenditures (3)		310,256		102,282		1,955		3,710		418,203



	Domestic Site		Int'l Site		Site		Not Identified
	Leasing		Leasing		Development		by Segment (1)		Total

Assets	(in thousands)
As of December 31, 2018	$	5,035,826	$	2,042,800	$	60,775	$	74,306	$	7,213,707
As of December 31, 2017	$	5,171,190	$	2,028,479	$	49,487	$	71,049	$	7,320,205

(1)Assets not identified by segment consist primarily of general corporate assets.

(2)Excludes depreciation, amortization, and accretion.

(3)Includes cash paid for capital expenditures and acquisitions and vehicle capital lease additions.

(4) International site leasing includes the impact of the $16,498 Oi reserve for the year ended December 31, 2016.

Other than Brazil, no foreign country represented a material amount of the Company’s total revenues in any of the periods presented. For the year ended December 31, 2018, 2017, and 2016, site leasing revenue in Brazil was $221.5 million, 217.4 million, and $178.3 million, respectively. Total long-lived assets in Brazil were $1,031.6 million and $1,278.9 million as of December 31, 2018, and 2017, respectively.

Quarterly Financial Data

12 Months Ended

Dec. 31, 2018

Quarterly Financial Data [Abstract]

Quarterly Financial Data

19.QUARTERLY FINANCIAL DATA (unaudited)



	Quarter Ended
	December 31,		September 30,		June 30,		March 31,
	2018		2018		2018		2018
	(in thousands, except per share amounts)
Revenues	$	483,849	$	467,221	$	456,322	$	458,303
Operating income		150,321		138,006		125,870		129,969
Depreciation, accretion, and amortization		(169,454)		(167,703)		(169,558)		(165,398)
Loss from extinguishment of debt, net		—		—		(13,798)		(645)
Net income (loss)		57,152		16,144		(57,392)		31,547

Net income (loss) per common share - basic	$	0.50	$	0.14	$	(0.50)	$	0.27
Net income (loss) per common share - diluted		0.50		0.14		(0.50)		0.27

	Quarter Ended
	December 31,		September 30,		June 30,		March 31,
	2017		2017		2017		2017
	(in thousands, except per share amounts)
Revenues	$	443,073	$	433,945	$	427,294	$	423,362
Operating income		119,081		117,011		114,590		107,819
Depreciation, accretion, and amortization		(162,643)		(161,907)		(159,520)		(159,030)
Loss from extinguishment of debt, net		—		—		(1,961)		—
Net income		7,660		49,161		9,233		37,600

Net income per common share - basic (1)	$	0.07	$	0.41	$	0.08	$	0.31
Net income per common share - diluted		0.06		0.41		0.08		0.31

(1)

The sums of quarterly earnings per share data may not equal annual data due to rounding.

Basic and diluted net income (loss) per share is computed by dividing net income (loss) by the weighted average number of shares for the period. Potentially dilutive instruments have been excluded from the computation of diluted loss per share as their impact would have been anti-dilutive.

Because net income (loss) per share amounts are calculated using the weighted average number of common and dilutive common shares outstanding during each quarter, the sum of the per share amounts for the four quarters may not equal the total loss per share amounts for the year.

Accrued Expenses

12 Months Ended

Dec. 31, 2018

Accrued Expenses [Abstract]

Accrued Expenses

20.ACCRUED EXPENSES

The Company’s accrued expenses are comprised of the following:



	As of		As of
	December 31, 2018		December 31, 2017

	(in thousands)
Salaries and benefits	$	16,015	$	13,506
Real estate and property taxes		7,928		7,125
Non-cash capital expenditures		12,387		12,408
Other		27,335		36,823
Total accrued expenses	$	63,665	$	69,862

Schedule III - Schedule of Real Estate and Accumulated Depreciation

12 Months Ended

Dec. 31, 2018

Schedule III - Schedule of Real Estate and Accumulated Depreciation [Abstract]

Schedule III - Schedule of Real Estate and Accumulated Depreciation

Schedule III—Schedule of Real Estate and Accumulated Depreciation

Gross

Life on Which

Cost

Amount

Accumulated

Depreciation

Capitalized

Carried

Depreciation

in Latest

Initial

Subsequent

at Close

Income

Cost to

to

of Current

Date of

Date

Statement is

Description

Encumbrances

Company

Acquisition

Period

Construction

Acquired

Computed

(in thousands)

29,578 sites

(1)

$

7,428,000

(2)

(3)

$

5,561,005

(4)

$

(2,868,507)

Various

Up to 20 years

(1)

No single site exceeds 5% of the aggregate gross amounts at which the assets were carried at the close of the period set forth in the table above.

(2)

As of December 31, 2018, certain assets secure debt of $7.4 billion.

(3)

The Company has omitted this information, as it would be impracticable to compile such information on a site-by-site basis.

(4)

Does not include those sites under construction.



	2018		2017		2016

	(in thousands)
Gross amount at beginning	$	5,340,858	$	5,079,660	$	4,839,874
Additions during period:
Acquisitions (1)		131,686		112,979		72,456
Construction and related costs on new builds		54,237		70,361		58,143
Augmentation and tower upgrades		49,201		43,288		37,861
Land buyouts and other assets		37,032		41,657		44,574
Tower maintenance		30,048		29,391		28,257
Other (2)		—		—		45,829
Total additions		302,204		297,676		287,120
Deductions during period:
Cost of real estate sold or disposed		(1,083)		(1,027)		(12,842)
Impairment		(17,130)		(34,101)		(34,492)
Other (2)		(63,844)		(1,350)		—
Total deductions		(82,057)		(36,478)		(47,334)
Balance at end	$	5,561,005	$	5,340,858	$	5,079,660

(1)

Inclusive of changes between the final purchase price allocation and the preliminary purchase price allocations.

(2)

Primarily represents cumulative translation adjustments related to changes in foreign currency exchange rates.



	2018		2017		2016

	(in thousands)
Gross amount of accumulated depreciation at beginning	$	(2,627,841)	$	(2,396,587)	$	(2,160,530)
Additions during period:
Depreciation		(257,469)		(248,818)		(254,982)
Other (1)		(25)		—		(5,557)
Total additions		(257,494)		(248,818)		(260,539)
Deductions during period:
Amount of accumulated depreciation for assets sold or disposed		4,392		17,051		24,482
Other (1)		12,436		513		—
Total deductions		16,828		17,564		24,482
Balance at end	$	(2,868,507)	$	(2,627,841)	$	(2,396,587)

(1)

Primarily represents cumulative translation adjustments related to changes in foreign currency exchange rates.

Summary of Significant Accounting Policies (Policy)

12 Months Ended

Dec. 31, 2018

Summary of Significant Accounting Policies [Abstract]

Principles of Consolidation

The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the Company and its majority and wholly-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. The significant estimates made by management relate to the allowance for doubtful accounts, the costs and revenue relating to the Company’s construction contracts, stock-based compensation assumptions, valuation allowance related to deferred tax assets, fair value of long-lived assets, the useful lives of towers and intangible assets, anticipated property tax assessments, fair value of investments and asset retirement obligations. Management develops estimates based on historical experience and on various assumptions about the future that are believed to be reasonable based on the information available. These estimates ultimately may differ from actual results and such differences could be material.

Cash and Cash Equivalents

Cash and cash equivalents consist primarily of cash in banks, money market funds, commercial paper, highly liquid short-term investments, and other marketable securities with an original maturity of three months or less at the time of purchase. These investments are carried at cost, which approximates fair value.

Restricted Cash

The Company classifies all cash pledged as collateral to secure certain obligations and all cash whose use is limited as restricted cash. This includes cash held in escrow to fund certain reserve accounts relating to the Tower Securities as well as for payment and performance bonds and surety bonds issued for the benefit of the Company in the ordinary course of business, as well as collateral associated with workers’ compensation plans (see Note 4).

Investments

Investment securities with original maturities of more than three months but less than one year at time of purchase are considered short-term investments. The Company’s short-term investments primarily consist of certificates of deposit with maturities of less than a year. Investment securities with maturities of more than a year are considered long-term investments and are classified in other assets on the accompanying Consolidated Balance Sheets. Long-term investments primarily consist of U.S. Treasuries, mutual funds, and preferred securities. Gross purchases and sales of the Company’s investments are presented within “Cash flows from investing activities” on the Company’s Consolidated Statements of Cash Flows.

The Company accounts for its investments in privately held companies under the equity method. The Company evaluates its investments for impairment at least annually. The Company determines the fair value of its investments by considering available evidence, including general market conditions, the investee’s financial condition, near-term prospects, market comparables and subsequent rounds of financing. The Company measures and records its investments at fair value when they are deemed to be other-than-temporarily impaired. The Company did not recognize any impairment loss associated with its investments during the years ended December 31, 2018, 2017, and 2016.

During the years ended December 31, 2018 and 2017, the Company received proceeds related to the sale or maturity of investments of $150.9 million and $0.2 million, respectively. During the year ended December 31, 2018 and 2017, no gain or loss was recorded related to the sale or maturity of investments. The proceeds are reflected in Net cash used in investing activities on the Consolidated Statements of Cash Flows. The aggregate carrying value of the Company’s investments was approximately $14.6 million and $8.6 million as of December 31, 2018 and 2017, respectively, and is classified within prepaid and other current assets and other assets on the Company’s consolidated balance sheets.

Property and Equipment

Property and equipment are recorded at cost or at estimated fair value (in the case of acquired properties), adjusted for asset impairment and estimated asset retirement obligations. Costs for self-constructed towers include direct materials and labor, indirect costs and capitalized interest. Approximately $0.9 million, $1.1 million, and $1.0 million of interest cost was capitalized in 2018, 2017 and 2016, respectively.

Depreciation on towers and related components is provided using the straight-line method over the estimated useful lives, not to exceed the minimum lease term of the underlying ground lease. The Company defines the minimum lease term as the shorter of the period from lease inception through the end of the term of all tenant lease obligations in existence at ground lease inception, including renewal periods, or the ground lease term, including renewal periods. If no tenant lease obligation exists at the date of ground lease inception, the initial term of the ground lease is considered the minimum lease term. Leasehold improvements are amortized on a straight-line basis over the shorter of the useful life of the improvement or the minimum lease term of the lease. For all other property and equipment, depreciation is provided using the straight-line method over the estimated useful lives.

The Company performs ongoing evaluations of the estimated useful lives of its property and equipment for depreciation purposes. The estimated useful lives are determined and continually evaluated based on the period over which services are expected to be rendered by the asset. If the useful lives of assets are reduced, depreciation may be accelerated in future years. Property and equipment under capital leases are amortized on a straight-line basis over the term of the lease or the remaining estimated life of the leased property, whichever is shorter, and the related amortization is included in depreciation expense. Expenditures for maintenance and repair are expensed as incurred.

Asset classes and related estimated useful lives are as follows:



Towers and related components	3 - 15 years
Furniture, equipment and vehicles	2 - 7 years
Buildings and improvements	10 - 30 years

Betterments, improvements, and significant repairs, which increase the value or extend the life of an asset, are capitalized and depreciated over the estimated useful life of the respective asset. Changes in an asset’s estimated useful life are accounted for prospectively, with the book value of the asset at the time of the change being depreciated over the revised remaining useful life. There has been no material impact for changes in estimated useful lives for any years presented.

Deferred Financing Fees

Financing fees related to the issuance of debt have been deferred and are being amortized using the effective interest rate method over the expected duration of the related indebtedness (see Note 12). For all of the Company’s debt, except for the Revolving Credit Facility where the debt issuance costs are being presented as an asset on the accompanying Consolidated Balance Sheet, debt issuance costs are presented on the balance sheet as a direct deduction from the related debt liability rather than as an asset.

Deferred Lease Costs

The Company defers certain initial direct costs associated with the origination of tenant leases and lease amendments and amortizes these costs over the initial lease term or over the lease term remaining if related to a lease amendment. Such deferred costs were approximately $11.3 million, $11.0 million, and $10.2 million in 2018, 2017, and 2016, respectively. Amortization expense was $12.2 million, $13.1 million, and $11.3 million for the years ended December 31, 2018, 2017 and 2016, respectively, and is included in cost of site leasing on the accompanying Consolidated Statements of Operations. As of December 31, 2018 and 2017, unamortized deferred lease costs were $27.0 million and $27.7 million, respectively, and are included in other assets on the accompanying Consolidated Balance Sheets.

Effective January 1, 2019, the Company adopted ASU 2016-02, Leases, which changed how deferred lease costs are calculated. Refer to “Recent Accounting Pronouncements Not Yet Adopted” for further changes related to the adoption of this guidance.

Intangible Assets

The Company classifies as intangible assets the fair value of current leases in place at the acquisition date of towers and related assets (referred to as the “Current contract intangibles”), and the fair value of future tenant leases anticipated to be added to the acquired towers (referred to as the “Network location intangibles”). These intangibles are estimated to have a useful life consistent with the useful life of the related tower assets, which is typically 15 years. For all intangible assets, amortization is provided using the straight-line method over the estimated useful lives as the benefit associated with these intangible assets is anticipated to be derived evenly over the life of the asset.

Impairment of Long-Lived Assets

The Company evaluates its individual long-lived and related assets with finite lives for indicators of impairment to determine when an impairment analysis should be performed. The Company evaluates its tower assets and Current contract intangibles at the tower level, which is the lowest level for which identifiable cash flows exists. The Company evaluates its Network location intangibles for impairment at the tower leasing business level whenever indicators of impairment are present. The Company has established a policy to at least annually evaluate its tower assets and Current contract intangibles for impairment.

The Company records an impairment charge when an investment in towers or related assets has been impaired, such that future undiscounted cash flows would not recover the then current carrying value of the investment in the tower and related intangible. If the future undiscounted cash flows are lower than the carrying value of the investment in the tower and related intangible, the Company calculates future discounted cash flows and compares those amounts to the carrying value. The Company records an impairment charge for any amounts lower than the carrying value. Estimates and assumptions inherent in the impairment evaluation include, but are not limited to, general market and economic conditions, historical operating results, geographic location, lease-up potential and expected timing of lease-up. In addition, the Company makes certain assumptions in determining an asset’s fair value for the purpose of calculating the amount of an impairment charge.

The Company recognized impairment charges of $27.1 million, $36.7 million, and $30.2 million for the years ended December 31, 2018, 2017 and 2016, respectively. Refer to Note 3 for further detail of these amounts.

Fair Value Measurements

The Company determines the fair market values 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. The following three levels of inputs 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.

Revenue Recognition and Accounts Receivable

Revenue from site leasing is recognized on a straight-line basis over the current term of the related lease agreements, which are generally five to ten years. Receivables recorded related to the straight-line impact of site leases are reflected in other assets on the Consolidated Balance Sheets. Rental amounts received in advance are recorded as deferred revenue on the Consolidated Balance Sheets. Revenues from site leasing represent 93% of the Company’s total revenues.

Site development projects in which the Company performs consulting services include contracts on a fixed price basis that are billed at contractual rates. Revenue is recognized over time based on milestones achieved, which are determined based on costs incurred. Amounts billed in advance (collected or uncollected) are recorded as deferred revenue on the Consolidated Balance Sheets.

Revenue from construction projects is recognized over time, determined by the percentage of cost incurred to date compared to management’s estimated total cost for each contract. This method is used because management considers total cost to be the best available measure of progress on the contracts. These amounts are based on estimates, and the uncertainty inherent in the estimates initially is reduced as work on the contracts nears completion. Refer to Note 9 for further detail of costs and estimated earnings in excess of billings on uncompleted contracts. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses are determined to be probable.

The site development segment represents approximately 7% of the Company’s total revenues. The Company accounts for site development revenue in accordance with ASC 606, Revenue from Contracts with Customers, which was adopted on January 1, 2018 by applying the modified retrospective transition method. Payment terms do not result in any significant financing arrangements. Furthermore, these contracts do not typically include variable consideration; therefore, the transaction price that is recognized over time is generally the amount of the total contract. The cumulative effect of initially applying the new revenue standard had no impact on the Company’s financial results. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The adoption of the new standard will have no impact to net income on an ongoing basis.

The accounts receivable balance was $111.0 million and $90.7 million as of December 31, 2018 and 2017, respectively, of which $27.1 million and $20.8 million related to the site development segment as of December 31, 2018 and 2017, respectively. Refer to Note 18 for further detail of the site development segment.

Allowance for Doubtful Accounts

The Company performs periodic credit evaluations of its customers. The Company monitors collections and payments from its customers and maintains a provision for estimated credit losses based upon historical experience, specific customer collection issues identified, and past due balances as determined based on contractual terms. Interest is charged on outstanding receivables from customers on a case by case basis in accordance with the terms of the respective contracts or agreements with those customers. Amounts determined to be uncollectible are written off against the allowance for doubtful accounts in the period in which uncollectibility is determined to be probable.

The following is a rollforward of the allowance for doubtful accounts:



	For the year ended December 31,
	2018		2017		2016

		(in thousands)
Beginning balance	$	26,481	$	24,518	$	1,681
Provision for doubtful accounts		551		2,909		22,516
Write-offs, net of recoveries		(591)		(647)		(614)
Currency translation adjustment		(2,561)		(299)		935
Ending balance	$	23,880	$	26,481	$	24,518

On June 20, 2016, Oi, S.A. (“Oi”), the Company’s largest customer in Brazil, filed a petition for judicial reorganization in Brazil. Prior to the filing of the reorganization petition, Oi was current in all payment obligations to the Company through April 30, 2016. Due to the uncertainty surrounding the recoverability of amounts owed by Oi relating to services provided prior to the date of Oi’s petition, the Company has recorded a $16.5 million bad debt provision (the “Oi reserve”) which covers amounts owed or potentially owed by Oi as of the filing date. The Oi reserve was recorded in Selling, general, and administrative expense on the consolidated statement of operations for the year ended December 31, 2016. Under Brazilian law governing judicial reorganizations, the contracts governing post-petition obligations such as tower rents remain unchanged, and debtors do not have the ability to reject or terminate the contracts other than pursuant to their original terms. Since the filing, the Company has received all rental payments due in connection with obligations of Oi accruing post-petition. On January 8, 2018, Oi’s reorganization plan was approved by the Brazilian courts and Oi is expected to fully resolve all its pre-petition obligations in accordance with the terms of the plan, which includes a 10% reduction in the receivable and four annual installment payments beginning in December 2019.

Cost of Revenue

Cost of site leasing revenue includes ground lease rent, property taxes, amortization of deferred lease costs, maintenance and other tower operating expenses. All ground lease rental obligations due to be paid out over the lease term, including fixed escalations, are recorded on a straight-line basis over the minimum lease term. Liabilities recorded related to the straight-lining of ground leases are reflected in other long-term liabilities on the Consolidated Balance Sheets. Cost of site development revenue includes the cost of materials, salaries and labor costs, including payroll taxes, subcontract labor, vehicle expense and other costs directly and indirectly related to the projects. All costs related to site development projects are recognized as incurred.

Income Taxes

The Company recognizes deferred tax assets and liabilities for the estimated future tax consequences attributable to differences between the financial reporting and tax bases of existing assets and liabilities. Deferred tax assets and liabilities are measured using tax rates in effect for the year in which the temporary differences are expected to reverse. A valuation allowance is recorded to reduce the carrying amounts of deferred tax assets if it is "more-likely-than-not" that those assets will not be realized. The Company considers many factors when assessing the likelihood of future realization, including the Company's recent cumulative earnings by taxing jurisdiction, expectations of future taxable income, prudent and feasible tax planning strategies that are available, the carryforward periods available to the Company for tax reporting purposes and other relevant factors.

The Company began operating as a REIT for federal income tax purposes effective January 1, 2016. As a REIT, the Company generally is not subject to corporate level federal income tax on taxable income it distributes to its stockholders as long as it meets the organizational and operational requirements under the REIT rules. However, certain subsidiaries have made an election with the IRS to be treated as a taxable REIT subsidiary (“TRS”) in conjunction with the Company's REIT election. The TRS elections permit SBA to engage in certain business activities in which the REIT may not engage directly, so long as these activities are conducted in entities that elect to be treated as TRSs under the Code. A TRS is subject to federal and state income taxes on the income from these activities. Additionally, the Company has included in TRSs the Company’s tower operations in most foreign jurisdictions; however, the REIT holds selected tower assets in Puerto Rico and USVI. Those operations will continue to be subject to foreign taxes in the jurisdiction in which such assets and operations are located regardless of whether they are included in a TRS.

The Company will continue to file separate federal tax returns for the REIT and TRS for the year ended December 31, 2018. The REIT had taxable income and utilized net operating losses (“NOLs”) to offset its 2018 distribution requirement. Some of our TRSs generated NOLs which will be carried forward to use in future years. The deferred tax asset generated by the NOLs are fully reserved by a valuation allowance.

The Company records a liability for unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in a tax return if applicable. The Company has not identified any tax exposures that require a reserve. To the extent that the Company records unrecognized tax exposures, any related interest and penalties will be recognized as interest expense in the Company’s Consolidated Statements of Operations.

Stock-Based Compensation

The Company measures and recognizes compensation expense for all share-based payment awards made to employees and directors, including stock options, restricted stock units and employee stock purchases under employee stock purchase plans. The Company records compensation expense, for stock options and restricted stock units on a straight-line basis over the vesting period. Compensation expense for employee stock options is based on the estimated fair value of the options on the date of the grant using the Black-Scholes option-pricing model. Compensation expense for restricted stock units is based on the fair market value of the units awarded at the date of the grant.

Asset Retirement Obligations

The Company has entered into ground leases for the land underlying the majority of the Company’s towers. A majority of these leases require the Company to restore land interests to their original condition upon termination of the ground lease.

The Company recognizes asset retirement obligations in the period in which they are incurred, if a reasonable estimate of a fair value can be made, and accretes such liability through the obligation’s estimated settlement date. The associated asset retirement costs are capitalized as part of the carrying amount of the related tower fixed assets, and over time, the liability is accreted to its present value each period and the capitalized cost is depreciated over the estimated useful life of the tower.

As of December 31, 2018 and 2017, the asset retirement obligation was $9.9 million and $7.2 million, respectively, and is included in other long-term liabilities on the Consolidated Balance Sheets. Upon settlement of the obligations, any difference between the cost to retire an asset and the recorded liability is recorded in the Consolidated Statements of Operations. In determining the measurement of the asset retirement obligations, the Company considered the nature and scope of the contractual restoration obligations contained in the Company’s ground leases, the historical retirement experience as an indicator of future restoration probabilities, intent in renewing existing ground leases through lease termination dates, current and future value and timing of estimated restoration costs and the credit adjusted risk-free rate used to discount future obligations.

Comprehensive Income (Loss)

Comprehensive income (loss) is defined as the change in equity (net assets) of a business enterprise during a period from transactions and other events and circumstances from non-owner sources, and is comprised of net income (loss) and other foreign currency adjustments.

Foreign Currency Translation

All assets and liabilities of foreign subsidiaries that do not utilize the U.S. dollar as its functional currency are translated at period-end rates of exchange, while revenues and expenses are translated at monthly average rates of exchange prevailing during the year. Unrealized remeasurement gains and losses are reported as foreign currency translation adjustments through Accumulated Other Comprehensive Loss in the accompanying Consolidated Statement of Shareholders’ Deficit.

For foreign subsidiaries where the U.S. dollar is the functional currency, monetary assets and liabilities of such subsidiaries, which are not denominated in U.S. dollars, are remeasured at exchange rates in effect at the balance sheet date, and revenues and expenses are remeasured at monthly average rates prevailing during the year. Unrealized translation gains and losses are reported as other income (expense), net in the Consolidated Statement of Operations.

Acquisitions

In January 2017, the FASB issued ASU 2017-01, Clarifying the Definition of a Business. ASU 2017-01 provides revised guidance to determine when an acquisition meets the definition of a business or when the acquisition should be accounted for as an asset acquisition. The Company adopted this standard effective January 1, 2017 and all changes are being accounted for prospectively. The adoption of ASU 2017-01 did not have a material impact on the Company’s unaudited consolidated financial statements and related disclosures.

Under the new standard, the Company’s acquisitions will generally qualify for asset acquisition treatment under ASC 360, Property, Plant, and Equipment, rather than business combination treatment under ASC 805 Business Combinations. For acquisitions, the aggregate purchase price is allocated on a relative fair value basis to towers and related intangible assets. The fair values of these net assets acquired are based on management’s estimates and assumptions, as well as other information compiled by management, including valuations that utilize customary valuation procedures and techniques. The fair value estimates are based on available historical information and on future expectations and assumptions deemed reasonable by management at the time. For acquisitions, if the actual results differ from the estimates and judgments used in these fair values, the amounts recorded in the consolidated financial statements could be subject to a possible impairment of the intangible assets, or require acceleration of the amortization expense of intangible assets in subsequent periods. For acquisitions, external, direct transaction costs will be capitalized as a component of the cost of the asset acquired. The Company will continue to expense internal acquisition costs as incurred. For business combinations, the estimates of the fair value of the assets acquired and liabilities assumed at the date of an acquisition are subject to adjustment during the measurement period (up to one year from the particular acquisition date). During the measurement period, the Company will adjust assets and/or liabilities if new information is obtained about facts and circumstances that existed as of the acquisition date that, if known, would have resulted in a revised estimated value of those assets and/or liabilities as of that date. As of December 31, 2018, there were no purchase price allocations that were preliminary.

In connection with certain acquisitions, the Company may agree to pay contingent consideration (or earnouts) in cash or stock if the communication sites or businesses that are acquired meet or exceed certain performance targets over a period of one to three years after they have been acquired. The Company accrues for contingent consideration in connection with business combinations at fair value as of the date of the acquisition. All subsequent changes in fair value of contingent consideration payable in cash are recorded through Consolidated Statements of Operations. Contingent consideration in connection with asset acquisitions will be recognized at the time when the contingency is resolved or becomes payable and will increase the cost basis of the assets acquired.

Intercompany Loans Subject to Remeasurement

The Company has two wholly owned subsidiaries, Brazil Shareholder I, LLC, a Florida limited liability company, and SBA Torres Brasil, Limitada, a limited liability company existing under the laws of the Republic of Brazil, which have entered into intercompany loan agreements pursuant to which the entities may from time to time agree to lend/borrow amounts under the terms of each agreement. The first agreement entered into in November 2014 was for $750.0 million and was created to fund the acquisition of 1,641 towers in Brazil. The second agreement entered into in December 2017 was for $500.0 million and was created to fund the acquisition of 941 towers in Brazil.

In accordance with Accounting Standards Codification (ASC) 830, the Company remeasures foreign denominated intercompany loans with the corresponding change in the balance being recorded in Other income (expense), net in the Consolidated Statement of Operations as settlement is anticipated or planned in the foreseeable future. For the years ended December 31, 2018, 2017, and 2016, the Company recorded a $89.1 million loss, a $8.8 million loss, and a $90.0 million gain, respectively, on the remeasurement of intercompany loans due to changes in foreign exchange rates. As of December 31, 2018 and 2017, the aggregate amount outstanding under the two intercompany loan agreements with the Company’s Brazilian subsidiary was $536.9 million and $560.9 million, respectively.

Recent Accounting Pronouncements not yet Adopted

Recent Accounting Pronouncements Not Yet Adopted

In February 2016, the FASB issued ASU 2016-02, Leases. The standard requires lessees to recognize a right-of-use asset and a lease liability, initially measured at the present value of the lease payments for all leases with a term greater than 12 months. The accounting for lessors remains largely unchanged from existing guidance. The Company has adopted this standard as of January 1, 2019. This guidance will have a material impact on the Company’s consolidated balance sheet due to the recognition of lease liabilities for its ground leases of approximately $2.3 billion to $2.7 billion. Adoption of this guidance will not have a significant impact on the Company’s lease classification, a material impact on its consolidated statement of operations, or a notable impact on its liquidity. Additionally, the standard will have no impact on the Company’s debt-covenant compliance under its current agreements.

In July 2018, the FASB issued additional guidance on the accounting for leases. The guidance provides companies with another transition method that allows entities to recognize a cumulative-effect adjustment to the opening balance of retained earnings as of the date of adoption. Under this method, previously presented years’ financial positions and results are not adjusted. The Company adopted this alternative transition method. The new guidance also provides lessors with a practical expedient, by class of underlying asset, to not separate non-lease components from the associated lease component if (1) the non-lease components would otherwise be accounted for under the new revenue recognition standard, (2) both the timing and pattern of transfer are the same for the non-lease components and associated lease component, and (3) if accounted for separately, the lease component would be classified as an operating lease. The Company adopted this practical expedient in its accounting for leases.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Summary of Significant Accounting Policies [Abstract]

Schedule of Asset Classes and Related Estimated Useful Lives



Towers and related components	3 - 15 years
Furniture, equipment and vehicles	2 - 7 years
Buildings and improvements	10 - 30 years

Allowance for Doubtful Accounts



	For the year ended December 31,
	2018		2017		2016

		(in thousands)
Beginning balance	$	26,481	$	24,518	$	1,681
Provision for doubtful accounts		551		2,909		22,516
Write-offs, net of recoveries		(591)		(647)		(614)
Currency translation adjustment		(2,561)		(299)		935
Ending balance	$	23,880	$	26,481	$	24,518

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Measurements [Abstract]

Summary of Asset Impairment and Decommission Costs



	For the year
	ended December 31,
	2018		2017		2016

Asset impairment (1)	$	14,350	$	15,389	$	19,217
Write-off of carrying value of decommissioned towers		10,795		16,861		12,967
Gain on sale of fiber assets (2)		—		—		(8,919)
Other (including third party decommission costs)		1,989		4,447		6,977
Total asset impairment and decommission costs	$	27,134	$	36,697	$	30,242

(1)Represents impairment charges resulting from the Company’s regular analysis of whether the future cash flows from certain towers are adequate to recover the carrying value of the investment in those towers.

(2)Gain recognized on the sale of fiber assets acquired in the 2012 Mobilitie transaction.

Restricted Cash (Tables)

12 Months Ended

Dec. 31, 2018

Restricted Cash [Abstract]

Schedule of Cash, Cash Equivalents and Restricted Cash



	As of		As of		As of
	December 31, 2018		December 31, 2017		December 31, 2016		Included on Balance Sheet

		(in thousands)
Cash and cash equivalents	$	143,444	$	68,783	$	146,109
Securitization escrow accounts		32,261		32,699		36,607	Restr. cash - current asset
Payment and performance bonds		203		225		179	Restr. cash - current asset
Surety bonds and workers compensation		2,392		2,588		3,075	Other assets - noncurrent
Total cash, cash equivalents, and restr. cash	$	178,300	$	104,295	$	185,970

Prepaid Expenses and Other Current Assets and Other Assets (Tables)

12 Months Ended

Dec. 31, 2018

Prepaid Expenses and Other Current Assets and Other Assets [Abstract]

Schedule of Prepaid Expense and Other Current Assets



	As of		As of
	December 31, 2018		December 31, 2017

		(in thousands)
Prepaid ground rent	$	34,276	$	32,505
Loan receivables		11,178		948
Other		17,672		16,263
Total prepaid expenses and other current assets	$	63,126	$	49,716

Schedule of Other Assets



	As of		As of
	December 31, 2018		December 31, 2017

		(in thousands)
Prepaid ground rent	$	263,694	$	220,493
Straight-line rent receivable		322,073		313,650
Loan receivables		49,255		52,383
Deferred lease costs, net		27,020		27,703
Deferred tax asset - long term		18,330		1,670
Other		41,661		34,296
Total other assets	$	722,033	$	650,195

Acquisitions (Tables)

12 Months Ended

Dec. 31, 2018

Acquisitions [Abstract]

Schedule of Acquisition Activity



	For the year ended December 31,
	2018		2017		2016
Tower acquisitions (number of towers)		1,316		1,425		531

Schedule of Acquisition Capital Expenditures



	For the year ended December 31,
	2018		2017		2016

		(in thousands)
Acquisitions of towers and related intangible assets (1)	$	406,699	$	392,902	$	214,686
Land buyouts and other assets (2)		45,130		48,645		62,149
Total cash acquisition capital expenditures	$	451,829	$	441,547	$	276,835

(1)

The year ended December 31, 2017 excludes $63.3 million of acquisition costs funded through the issuance of 487,963 shares of Class A common stock.

(2)

In addition, the Company paid $24.3 million, $18.8 million, and $14.1 million for ground lease extensions and term easements on land underlying the Company’s towers during the years ending December 31, 2018, 2017, and 2016, respectively. The Company recorded these amounts in prepaid rent on its Consolidated Balance Sheets.

Intangible Assets, Net (Tables)

12 Months Ended

Dec. 31, 2018

Intangible Assets, Net [Abstract]

Gross and Net Carrying Amounts for each Major Class of Intangible Assets



	As of December 31, 2018						As of December 31, 2017
	Gross carrying		Accumulated		Net book		Gross carrying		Accumulated		Net book
	amount		amortization		value		amount		amortization		value

	(in thousands)
Current contract intangibles	$	4,394,416	$	(1,928,030)	$	2,466,386	$	4,355,171	$	(1,673,270)	$	2,681,901
Network location intangibles		1,669,859		(804,780)		865,079		1,617,441		(701,211)		916,230
Intangible assets, net	$	6,064,275	$	(2,732,810)	$	3,331,465	$	5,972,612	$	(2,374,481)	$	3,598,131

Estimated Future Amortization Expense



For the year ended December 31,	(in thousands)

2019	$	403,371
2020		402,447
2021		369,864
2022		349,657
2023		327,181

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2018

Property and Equipment, Net [Abstract]

Property and Equipment, Net (Including Assets Held Under Capital Leases)



	As of		As of
	December 31, 2018		December 31, 2017

	(in thousands)
Towers and related components	$	4,951,321	$	4,772,807
Construction-in-process		35,756		34,689
Furniture, equipment, and vehicles		54,814		53,260
Land, buildings, and improvements		668,459		630,370
Total property and equipment		5,710,350		5,491,126
Less: accumulated depreciation		(2,923,995)		(2,678,780)
Property and equipment, net	$	2,786,355	$	2,812,346

Costs and Estimated Earnings on Uncompleted Contracts (Tables)

12 Months Ended

Dec. 31, 2018

Costs and Estimated Earnings on Uncompleted Contracts [Abstract]

Summary of Costs and Estimated Earnings on Uncompleted Contracts



	As of		As of
	December 31, 2018		December 31, 2017

	(in thousands)
Costs incurred on uncompleted contracts	$	38,464	$	31,404
Estimated earnings		16,655		10,541
Billings to date		(31,952)		(24,771)
	$	23,167	$	17,174

Costs and Estimated Earnings on Uncompleted Contracts Accompanying Consolidated Balance Sheets



	As of		As of
	December 31, 2018		December 31, 2017

	(in thousands)
Costs and estimated earnings in excess of billings on uncompleted contracts	$	23,785	$	17,437
Billings in excess of costs and estimated earnings on
uncompleted contracts (included in Other current liabilities)		(618)		(263)
	$	23,167	$	17,174

Concentration of Credit Risk (Tables)

12 Months Ended

Dec. 31, 2018

Concentration of Credit Risk [Abstract]

Summary of Significant Customers and Percentage of Total Revenue for Specified Time Periods Derived from such Customers

The following is a list of significant customers (representing at least 10% of revenue for any period reported) and the percentage of total revenue for the specified time periods derived from such customers:



	For the year ended December 31,
Percentage of Total Revenues	2018	2017	2016

AT&T Wireless	24.0%	25.0%	25.7%
Sprint	17.9%	15.1%	16.1%
T-Mobile	16.4%	16.5%	17.0%
Verizon Wireless	14.7%	15.2%	15.2%

The Company’s site leasing and site development segments derive revenue from these customers. Client percentages of total revenue in each of the segments are as follows:



	For the year ended December 31,
Percentage of Domestic Site Leasing Revenue	2018	2017	2016

AT&T Wireless	31.9%	32.7%	32.7%
T-Mobile	20.3%	19.7%	19.6%
Sprint	19.6%	18.9%	19.8%
Verizon Wireless	19.0%	19.0%	18.2%

	For the year ended December 31,
Percentage of International Site Leasing Revenue	2018	2017	2016

Oi S.A.	35.5%	42.2%	43.9%
Telefonica	26.7%	25.7%	26.4%
Claro	11.4%	10.0%	9.4%



	For the year ended December 31,
Percentage of Site Development Revenue	2018	2017	2016

Sprint	47.1%	12.9%	11.7%
T-Mobile	16.4%	26.9%	28.4%
Verizon Wireless	6.4%	12.8%	16.5%
Nokia, Inc.	3.2%	10.1%	7.1%

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Weighted-Average Shares of Common Stock Outstanding used in Calculation of Basic and Diluted Earnings Per Share



	For the year ended December 31,
	2018		2017		2016
Numerator:
Net income	$	47,451	$	103,654	$	76,238
Denominator:
Basic weighted-average shares outstanding		114,909		119,860		124,448
Dilutive impact of stock options and restricted shares		1,606		1,162		696
Diluted weighted-average shares outstanding		116,515		121,022		125,144
Net income per common share:
Basic	$	0.41	$	0.86	$	0.61
Diluted	$	0.41	$	0.86	$	0.61

Debt (Tables)

12 Months Ended

Dec. 31, 2018

Debt [Abstract]

Schedule of Principal Values, Fair Values, and Carrying Values of Debt



		As of						As of
		December 31, 2018						December 31, 2017
	Maturity Date	Principal Balance		Fair Value		Carrying Value		Principal Balance		Fair Value		Carrying Value
2014 Senior Notes	Jul. 15, 2022	$	750,000	$	735,000	$	741,273	$	750,000	$	770,625	$	739,079
2016 Senior Notes	Sep. 1, 2024		1,100,000		1,034,000		1,083,689		1,100,000		1,127,500		1,081,262
2017 Senior Notes	Oct. 1, 2022		750,000		712,500		743,099		750,000		750,938		741,437
2013-1C Tower Securities	Apr. 10, 2018		—		—		—		425,000		423,853		424,482
2013-2C Tower Securities	Apr. 11, 2023		575,000		569,164		569,715		575,000		578,433		568,609
2013-1D Tower Securities	Apr. 10, 2018		—		—		—		330,000		330,145		329,585
2014-1C Tower Securities	Oct. 8, 2019		920,000		914,241		917,728		920,000		915,216		914,929
2014-2C Tower Securities	Oct. 8, 2024		620,000		609,665		614,315		620,000		620,942		613,461
2015-1C Tower Securities	Oct. 8, 2020		500,000		496,640		495,737		500,000		496,840		493,474
2016-1C Tower Securities	Jul. 9, 2021		700,000		691,432		694,994		700,000		691,166		693,118
2017-1C Tower Securities	Apr. 11, 2022		760,000		744,496		753,028		760,000		751,404		751,076
2018-1C Tower Securities	Mar. 9, 2023		640,000		641,478		632,725		—		—		—
Revolving Credit Facility	Apr. 11, 2023		325,000		325,000		325,000		40,000		40,000		40,000
2014 Term Loan	Mar. 24, 2021		—		—		—		1,447,500		1,451,119		1,439,373
2015 Term Loan	Jun. 10, 2022		—		—		—		487,500		488,109		480,801
2018 Term Loan	Apr. 11, 2025		2,388,000		2,262,630		2,367,250		—		—		—
Total debt		$	10,028,000	$	9,736,246	$	9,938,553	$	9,405,000	$	9,436,290	$	9,310,686
Less: current maturities of long-term debt							(941,728)						(20,000)
Total long-term debt, net of current maturities						$	8,996,825					$	9,290,686

Schedule of Future Principal Payment Obligations



For the year ended December 31,	(in thousands)
2019	$	944,000
2020		524,000
2021		724,000
2022		2,284,000
2023		1,564,000

Schedule of Cash and Non-Cash Interest Expense



	For the year ended December 31,
	2018				2017				2016
	Cash		Non-cash		Cash		Non-cash		Cash		Non-cash
	Interest		Interest		Interest		Interest		Interest		Interest

	(in thousands)
5.625% Senior Notes		—		—		—		—		21,094		—
5.75% Senior Notes		—		—		—		—		28,494		—
2014 Senior Notes		36,563		761		36,563		724		36,563		689
2016 Senior Notes		53,625		1,003		53,625		954		20,258		348
2017 Senior Notes		30,000		—		6,500		—		—		—
2010-2C Tower Securities		—		—		—		—		15,213		—
2012 Tower Securities		—		—		5,330		—		18,107		—
2013 Tower Securities		25,654		—		43,217		—		43,217		—
2014 Tower Securities		51,138		—		51,138		—		51,138		—
2015-1C Tower Securities		15,939		—		15,939		—		15,939		—
2016-1C Tower Securities		20,361		—		20,361		—		9,898		—
2017-1C Tower Securities		24,354		—		17,182		—		—		—
2018-1C Tower Securities		18,072		—		—		—		—		—
Revolving Credit Facility		7,411		—		8,046		—		4,167		—
2014 Term Loan		15,550		146		49,414		525		48,962		510
2015 Term Loan		5,237		187		16,641		676		16,487		656
2018 Term Loan		72,648		543		—		—		—		—
Capitalized interest and other		(335)		—		(207)		—		(366)		—
Total	$	376,217	$	2,640	$	323,749	$	2,879	$	329,171	$	2,203

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Stock-Based Compensation [Abstract]

Schedule of Assumptions Used to Estimate Fair Value of Stock Options



	For the year ended December 31,
	2018	2017	2016

Risk free interest rate	2.57% - 2.92%	1.70% - 1.97%	1.11% - 1.43%
Dividend yield	0.7%	0.0%	0.0%
Expected volatility	21.6%	20.0%	20.0%
Expected lives	4.6 years	4.6 years	4.7 years

Summary of Stock Option Activity



		Weighted-		Weighted-Average
		Average		Remaining
	Number	Exercise Price		Contractual	Aggregate
	of Shares	Per Share		Life (in years)	Intrinsic Value
Outstanding at December 31, 2015	3,794	$	84.66
Granted	1,357	$	96.64
Exercised	(603)	$	46.03
Forfeited/canceled	(101)	$	105.37
Outstanding at December 31, 2016	4,447	$	93.09
Granted	1,171	$	115.41
Exercised	(709)	$	80.73
Forfeited/canceled	(67)	$	105.81
Outstanding at December 31, 2017	4,842	$	100.12
Granted	941	$	156.55
Exercised	(926)	$	81.73
Forfeited/canceled	(41)	$	123.98
Outstanding at December 31, 2018	4,816	$	114.48	4.2	$	228,248
Exercisable at December 31, 2018	2,162	$	100.15	3.0	$	133,490
Unvested at December 31, 2018	2,654	$	126.17	5.1	$	94,758

Additional Information Regarding Options Outstanding And Exercisable



	Options Outstanding				Options Exercisable
		Weighted Average	Weighted			Weighted
		Remaining	Average			Average
Range	Outstanding	Contractual Life	Exercise Price		Exercisable	Exercise Price
	(in thousands)	(in years)			(in thousands)
$0.00 - $90.00	406	1.0	$	68.96	406	$	68.96
$90.01 - $110.00	1,609	3.5	$	96.29	983	$	96.08
$110.01 - $145.00	1,871	4.4	$	119.15	773	$	121.69
$145.01 - $175.00	930	6.2	$	156.55	—	$	0.00
	4,816				2,162

Summary of Activity of Options Outstanding not yet Vested



		Weighted-
		Average
	Number	Fair Value
	of Shares	Per Share
	(in thousands)
Unvested as of December 31, 2017	2,860	$	22.08
Shares granted	941	$	33.01
Vesting during period	(1,104)	$	21.74
Forfeited/canceled	(43)	$	26.32
Unvested as of December 31, 2018	2,654	$	26.05

Summary of Restricted Stock Unit Activity



		Weighted-Average
	Number of	Grant Date Fair
	Shares	Value per Share
	(in thousands)
Outstanding at December 31, 2017	328	$	110.20
Granted	138	$	156.61
Vested	(129)	$	110.93
Forfeited/canceled	(13)	$	135.22
Outstanding at December 31, 2018	324	$	128.69

Schedule of Non-Cash Compensation Expense



		For the year ended December 31,
	2018		2017		2016
	(in thousands)
Cost of revenues	$	1,182	$	1,013	$	418
Selling, general and administrative		41,145		37,236		32,497
Total cost of non-cash compensation included
in loss before provision for income taxes		42,327		38,249		32,915
Amount of income tax recognized in earnings		—		—		—
Amount charged against loss	$	42,327	$	38,249	$	32,915

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Taxes [Abstract]

Income (Loss) before Provision for Income Taxes from Continuing Operations by Geographic Area



		For the year ended December 31,
	2018		2017		2016

	(in thousands)
Domestic	$	99,203	$	73,405	$	(28,671)
Foreign		(47,519)		43,486		115,974
Total	$	51,684	$	116,891	$	87,303

Components of Provision for Income Taxes



		For the year ended December 31,
	2018		2017		2016

	(in thousands)
Current provision:
State	$	5,764	$	5,513	$	1,535
Foreign		13,756		11,681		8,121
Total current		19,520		17,194		9,656

Deferred provision (benefit) for taxes:
Federal		(9,463)		18,736		170,177
State		(1,412)		(241)		22,992
Foreign		(16,673)		9,155		30,425
Change in valuation allowance		12,261		(31,607)		(222,185)
Total deferred		(15,287)		(3,957)		1,409
Total provision for income taxes	$	4,233	$	13,237	$	11,065

Income Tax Rate Reconciliation


	For the year ended December 31,
	2018		2017		2016

	(in thousands)
Statutory federal expense	$	10,854	$	40,912	$	30,555
Rate and permanent differences on non-U.S. earnings (1)		3,620		3,690		(4,739)
State and local tax expense		4,824		5,415		3,941
REIT adjustment		(22,241)		(34,346)		205,317
Permanent differences		437		(1,365)		(3,577)
Tax Act impact on deferred taxes		(6,040)		31,547		—
Other		518		(1,009)		1,753
Valuation allowance		12,261		(31,607)		(222,185)
Provision for income taxes	$	4,233	$	13,237	$	11,065

(1)

This item includes the effect of foreign exchange rate changes which were previously shown on a separate line.

Components of Net Deferred Income Tax Asset and Liability



	As of December 31,
	2018			2017

	(in thousands)
Noncurrent deferred tax assets:
Net operating losses	$	63,622	$	65,257
Property, equipment, and intangible basis differences		4,793		3,038
Accrued liabilities		9,659		11,933
Non-cash compensation		16,641		7,500
Deferred revenue		2,005		2,110
Allowance for doubtful accounts		5,691		5,978
Currency translation		56,604		34,895
Other		2,480		2,698
Valuation allowance		(50,628)		(38,802)
Total noncurrent deferred tax assets, net (1)		110,867		94,607

Noncurrent deferred tax liabilities:
Property, equipment, and intangible basis differences		(114,652)		(98,589)
Straight-line rents		(20,469)		(22,740)
Deferred foreign withholding taxes		(6,225)		—
Deferred lease costs		(2,192)		(2,242)
Other		(123)		(136)
Total noncurrent deferred tax liabilities, net (1)	$	(32,794)	$	(29,100)

(1)Of these amounts, $18,330 and $51,124 are included in Other assets and Other long-term liabilities, respectively on the accompanying Consolidated Balance Sheets as of December 31, 2018. As of December 31, 2017, $1,670 and $30,770 are included in Other assets and Other long-term liabilities on the accompanying Consolidated Balance Sheet.

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies [Abstract]

Annual Minimum Lease Payments



For the year ended December 31,	Capital Leases		Operating Leases
2019	$	883	$	237,730
2020		482		239,208
2021		303		241,090
2022		86		242,320
2023		—		243,476
Total minimum lease payments		1,754
Less: amount representing interest		(83)
Present value of future payments		1,671
Less: current obligations		(860)
Long-term obligations	$	811

Annual Minimum Tower Lease Income



For the year ended December 31,	(in thousands)
2019	$	1,529,902
2020		1,326,108
2021		1,075,675
2022		815,219
2023		598,987

Segment Data (Tables)

12 Months Ended

Dec. 31, 2018

Segment Data [Abstract]

Schedule of Segment Reporting Information



	Domestic Site		Int'l Site		Site		Not Identified
	Leasing		Leasing		Development		by Segment		Total

For the year ended December 31, 2018	(in thousands)
Revenues	$	1,400,095	$	340,339	$	125,261	$	—	$	1,865,695
Cost of revenues (2)		266,131		106,165		96,499		—		468,795
Operating profit		1,133,964		234,174		28,762		—		1,396,900
Selling, general, and administrative		72,879		27,082		16,215		26,350		142,526
Acquisition related adjustments and expenses		5,268		5,693		—		—		10,961
Asset impairment and decommission costs		18,857		7,932		345		—		27,134
Depreciation, amortization and accretion		511,823		151,570		2,556		6,164		672,113
Operating income (loss)		525,137		41,897		9,646		(32,514)		544,166
Other expense (principally interest expense
and other expense)								(492,482)		(492,482)
Income before provision for income taxes										51,684
Cash capital expenditures (3)		338,610		258,785		1,561		3,724		602,680
For the year ended December 31, 2017
Revenues	$	1,308,389	$	314,784	$	104,501	$	—	$	1,727,674
Cost of revenues (2)		260,826		98,701		86,785		—		446,312
Operating profit		1,047,563		216,083		17,716		—		1,281,362
Selling, general, and administrative		67,263		24,320		15,433		23,681		130,697
Acquisition related adjustments and expenses		8,171		4,196		—		—		12,367
Asset impairment and decommission costs		29,523		6,994		180		—		36,697
Depreciation, amortization and accretion		498,842		135,155		2,580		6,523		643,100
Operating income (loss)		443,764		45,418		(477)		(30,204)		458,501
Other expense (principally interest expense
and other expense)								(341,610)		(341,610)
Income before provision for income taxes										116,891
Cash capital expenditures (3)		225,074		358,691		1,221		3,859		588,845
For the year ended December 31, 2016
Revenues	$	1,273,866	$	264,204	$	95,055	$	—	$	1,633,125
Cost of revenues (2)		260,941		81,274		78,682		—		420,897
Operating profit		1,012,925		182,930		16,373		—		1,212,228
Selling, general, and administrative (4)		72,701		35,897		13,039		21,712		143,349
Acquisition related adjustments and expenses		6,233		6,907		—		—		13,140
Asset impairment and decommission costs		26,073		1,824		—		2,345		30,242
Depreciation, amortization and accretion		509,108		119,466		3,402		6,213		638,189
Operating income (loss)		398,810		18,836		(68)		(30,270)		387,308
Other expense (principally interest expense
and other expense)								(300,005)		(300,005)
Income before provision for income taxes										87,303
Cash capital expenditures (3)		310,256		102,282		1,955		3,710		418,203



	Domestic Site		Int'l Site		Site		Not Identified
	Leasing		Leasing		Development		by Segment (1)		Total

Assets	(in thousands)
As of December 31, 2018	$	5,035,826	$	2,042,800	$	60,775	$	74,306	$	7,213,707
As of December 31, 2017	$	5,171,190	$	2,028,479	$	49,487	$	71,049	$	7,320,205

(1)Assets not identified by segment consist primarily of general corporate assets.

(2)Excludes depreciation, amortization, and accretion.

(3)Includes cash paid for capital expenditures and acquisitions and vehicle capital lease additions.

(4) International site leasing includes the impact of the $16,498 Oi reserve for the year ended December 31, 2016.

Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Data [Abstract]

Schedule of Quarterly Financial Information


	Quarter Ended
	December 31,		September 30,		June 30,		March 31,
	2018		2018		2018		2018
	(in thousands, except per share amounts)
Revenues	$	483,849	$	467,221	$	456,322	$	458,303
Operating income		150,321		138,006		125,870		129,969
Depreciation, accretion, and amortization		(169,454)		(167,703)		(169,558)		(165,398)
Loss from extinguishment of debt, net		—		—		(13,798)		(645)
Net income (loss)		57,152		16,144		(57,392)		31,547

Net income (loss) per common share - basic	$	0.50	$	0.14	$	(0.50)	$	0.27
Net income (loss) per common share - diluted		0.50		0.14		(0.50)		0.27

	Quarter Ended
	December 31,		September 30,		June 30,		March 31,
	2017		2017		2017		2017
	(in thousands, except per share amounts)
Revenues	$	443,073	$	433,945	$	427,294	$	423,362
Operating income		119,081		117,011		114,590		107,819
Depreciation, accretion, and amortization		(162,643)		(161,907)		(159,520)		(159,030)
Loss from extinguishment of debt, net		—		—		(1,961)		—
Net income		7,660		49,161		9,233		37,600

Net income per common share - basic (1)	$	0.07	$	0.41	$	0.08	$	0.31
Net income per common share - diluted		0.06		0.41		0.08		0.31

(1)

The sums of quarterly earnings per share data may not equal annual data due to rounding.

Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2018

Accrued Expenses [Abstract]

Schedule of Accrued Expenses



	As of		As of
	December 31, 2018		December 31, 2017

	(in thousands)
Salaries and benefits	$	16,015	$	13,506
Real estate and property taxes		7,928		7,125
Non-cash capital expenditures		12,387		12,408
Other		27,335		36,823
Total accrued expenses	$	63,665	$	69,862

General (Narrative) (Details)	12 Months Ended
General (Narrative) (Details)	Dec. 31, 2018 item
Company owned tower sites	29,578
Domestic [Member]
Company owned tower sites	16,263
International [Member]
Company owned tower sites	13,315

Summary of Significant Accounting Policies (Narrative) (Details)	1 Months Ended		12 Months Ended
	Dec. 31, 2017 USD ($) item	Nov. 30, 2014 USD ($) item	Dec. 31, 2018 USD ($) item entity	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($) item
Summary of Significant Accounting Policies [Line Items]
Cost-method investments, impairment loss			$ 0	$ 0	$ 0
Proceeds from sale of other investments			150,900,000	200,000
Gain on sale of investments			0	0
Cost-method investments, carrying value	$ 8,600,000		14,600,000	8,600,000
Interest cost capitalized			900,000	1,100,000	1,000,000
Deferred lease costs	11,000,000		11,300,000	11,000,000	10,200,000
Amortization expense	13,100,000		12,200,000	13,100,000	11,300,000
Unamortized deferred lease costs	27,700,000		$ 27,000,000	27,700,000
Intangible assets, useful life			15 years
Impairment charge recognized, related to long-lived assets			$ 27,100,000	36,700,000	$ 30,200,000
Accounts receivable, net	90,673,000		111,035,000	90,673,000
Asset retirement obligation	7,200,000		$ 9,900,000	$ 7,200,000
Number of wholly owned subsidiaries that entered into intercompany loan agreement \| entity			2
Intercompany loan maximum lend/borrow amount	$ 500,000,000	$ 750,000,000
Number of towers acquired \| item	941	1,641	1,316	1,425	531
Gain (loss) on remeasurement of U.S. dollar denominated intercompany loan			$ (89,101,000)	$ (8,754,000)	$ 90,030,000
Intercompany foreign currency outstanding balance	$ 560,900,000		$ 536,900,000	560,900,000
Oi S.A. [Member]
Summary of Significant Accounting Policies [Line Items]
Percentage reduction in accounts receivable due to customer reorganization plan			10.00%
Number of annual installment payments \| item			4
Minimum [Member] \| Accounting Standards Update 2016-02 [Member]
Summary of Significant Accounting Policies [Line Items]
Lease liability			$ 2,300,000,000
Maximum [Member] \| Accounting Standards Update 2016-02 [Member]
Summary of Significant Accounting Policies [Line Items]
Lease liability			2,700,000,000
Site Development [Member]
Summary of Significant Accounting Policies [Line Items]
Accounts receivable, net	$ 20,800,000		$ 27,100,000	$ 20,800,000
Site Development [Member] \| Revenue [Member]
Summary of Significant Accounting Policies [Line Items]
Concentration risk percentage			7.00%

Summary of Significant Accounting Policies (Schedule of Asset Classes and Related Estimated Useful Lives) (Details)	12 Months Ended
	Dec. 31, 2018
Towers and Related Components [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Towers and Related Components [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	15 years
Furniture, Equipment and Vehicles [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	2 years
Furniture, Equipment and Vehicles [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	7 years
Buildings and improvements [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	10 years
Buildings and improvements [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	30 years

Summary of Significant Accounting Policies (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of Significant Accounting Policies [Abstract]
Beginning balance	$ 26,481	$ 24,518	$ 1,681
Provision for doubtful accounts	551	2,909	22,516
Write-offs, net of recoveries	(591)	(647)	(614)
Currency translation adjustment	(2,561)	(299)	935
Ending balance	$ 23,880	$ 26,481	$ 24,518

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accrued earnouts	$ 500	$ 2,500
Performance targets, maximum potential obligation	13,300	11,100
Treasury securities	200	200
Held-to-maturity investments, carrying value	200	500
Held-to-maturity investments, fair value	200	500
Purchase of investments	(156,983)	(397)	$ (100)
Proceeds from sale of investments	150,890	231	$ 712
Business Combinations and Asset Acquisitions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Performance targets, maximum potential obligation	$ 700	$ 3,100
Revolving Credit Facility [Member] \| Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Basis spread on variable interest rate	1.125%
Revolving Credit Facility [Member] \| Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Basis spread on variable interest rate	1.75%

Fair Value Measurements (Summary of Asset Impairment and Decommission Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Asset impairment	$ 14,350	$ 15,389	$ 19,217
Other (including third party decommission costs)	1,989	4,447	6,977
Total asset impairment and decommission costs	27,134	36,697	30,242
Fiber Assets [Member]
Gain on sale of fiber assets			(8,919)
Decommissioned Towers [Member]
Write-off carrying value of decommissioned towers	$ 10,795	$ 16,861	$ 12,967

Restricted Cash (Narrative) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Surety, Payment and Performance Bonds [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Surety, payment and performance bonds	$ 40,500,000	$ 39,500,000
Collateral	0	0
Workers Compensation Policy [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Collateral	$ 2,200,000	$ 2,500,000

Restricted Cash (Schedule of Cash, Cash Equivalents and Restricted Cash) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted Cash And Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 143,444	$ 68,783	$ 146,109
Restricted cash - current asset	32,464	32,924
Total cash, cash equivalents, and restricted cash	178,300	104,295	185,970	$ 146,619
Securitization Escrow Accounts [Member] \| Restricted Cash - Current Asset [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - current asset	32,261	32,699	36,607
Payment and Performance Bonds [Member] \| Restricted Cash - Current Asset [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Cash and cash equivalents	203	225	179
Surety Bonds and Workers Compensation [Member] \| Other Assets - Noncurrent [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash - noncurrent asset	$ 2,392	$ 2,588	$ 3,075

Prepaid Expenses and Other Current Assets and Other Assets (Schedule of Prepaid Expense and Other Current Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Prepaid Expenses and Other Current Assets and Other Assets [Abstract]
Prepaid ground rent	$ 34,276	$ 32,505
Loan receivables	11,178	948
Other	17,672	16,263
Total prepaid expenses and other current assets	$ 63,126	$ 49,716

Prepaid Expenses and Other Current Assets and Other Assets (Schedule Of Other Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Prepaid Expenses and Other Current Assets and Other Assets [Abstract]
Prepaid ground rent	$ 263,694	$ 220,493
Straight-line rent receivable	322,073	313,650
Loan receivables	49,255	52,383
Deferred lease costs, net	27,020	27,703
Deferred tax asset - long term	18,330	1,670
Other	41,661	34,296
Total other assets	$ 722,033	$ 650,195

Acquisitions (Narrative) (Details) $ in Millions	1 Months Ended			12 Months Ended
Acquisitions (Narrative) (Details) $ in Millions	Jan. 31, 2019 USD ($) item	Dec. 31, 2017 USD ($) item	Nov. 30, 2014 item	Dec. 31, 2018 USD ($) item	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($) item
Business Acquisition [Line Items]
Number of towers acquired \| item		941	1,641	1,316	1,425	531
Cash paid for acquisition						$ 214.7
Property and equipment						72.8
Intangible assets						144.4
Working capital adjustments						$ 2.5
Other Acquisitions [Member]
Business Acquisition [Line Items]
Number of towers acquired \| item				1,316	1,425
Property and equipment		$ 114.7		$ 134.5	$ 114.7
Intangible assets		345.3		280.7	345.3
Working capital adjustments		$ 3.8		$ 8.5	$ 3.8
Subsequent Event [Member]
Business Acquisition [Line Items]
Number of towers acquired \| item	27
Cash paid for acquisition	$ 10.7

Acquisitions (Schedule of Acquisition Activity) (Details) - item	1 Months Ended		12 Months Ended
	Dec. 31, 2017	Nov. 30, 2014	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquisitions [Abstract]
Tower acquisitions (number of towers)	941	1,641	1,316	1,425	531

Acquisitions (Schedule of Acquisition Capital Expenditures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquisitions [Abstract]
Acquisitions of towers and related intangible assets	$ 406,699	$ 392,902	$ 214,686
Land buyouts and other assets	45,130	48,645	62,149
Total cash acquisition capital expenditures	451,829	441,547	276,835
Acquisition costs paid through the issuance of common stock		$ 63,300
Common stock issued for acquisition costs		487,963
Ground lease extensions	$ 24,300	$ 18,800	$ 14,100

Intangible Assets, Net (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Intangible Assets, Net [Abstract]
Intangible assets, useful life	15 years
Amortization expense	$ 402.6	$ 384.1	$ 369.9

Intangible Assets, Net (Gross and Net Carrying Amounts for each Major Class of Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 6,064,275	$ 5,972,612
Accumulated amortization	(2,732,810)	(2,374,481)
Net book value	3,331,465	3,598,131
Current Contract Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	4,394,416	4,355,171
Accumulated amortization	(1,928,030)	(1,673,270)
Net book value	2,466,386	2,681,901
Network Location Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	1,669,859	1,617,441
Accumulated amortization	(804,780)	(701,211)
Net book value	$ 865,079	$ 916,230

Intangible Assets, Net (Estimated Future Amortization Expense) (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Intangible Assets, Net [Abstract]
2019	$ 403,371
2020	402,447
2021	369,864
2022	349,657
2023	$ 327,181

Property and Equipment, Net (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property and Equipment, Net [Abstract]
Depreciation expense	$ 269.2	$ 258.4	$ 268.1
Non-cash capital expenditures	$ 12.4

Property and Equipment, Net (Property and Equipment, Net (Including Assets Held Under Capital Leases)) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 5,710,350	$ 5,491,126
Less: accumulated depreciation	(2,923,995)	(2,678,780)
Property and equipment, net	2,786,355	2,812,346
Towers and Related Components [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	4,951,321	4,772,807
Construction-In-Process [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	35,756	34,689
Furniture, Equipment and Vehicles [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	54,814	53,260
Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 668,459	$ 630,370

Costs and Estimated Earnings on Uncompleted Contracts (Narrative) (Details) - customer	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Costs and Estimated Earnings on Uncompleted Contracts [Abstract]
Costs and estimated earnings in excess of billings on uncompleted contracts, net of billings in excess of costs and estimated earnings, percentage comprised by significant customers	96.30%	87.90%
Number of significant customers	8	8

Costs and Estimated Earnings on Uncompleted Contracts (Summary of Costs and Estimated Earnings on Uncompleted Contracts) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Costs and Estimated Earnings on Uncompleted Contracts [Abstract]
Costs incurred on uncompleted contracts	$ 38,464	$ 31,404
Estimated earnings	16,655	10,541
Billings to date	(31,952)	(24,771)
Costs and estimated earnings on uncompleted contracts	$ 23,167	$ 17,174

Costs and Estimated Earnings on Uncompleted Contracts (Costs and Estimated Earnings on Uncompleted Contracts Accompanying Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Costs and Estimated Earnings on Uncompleted Contracts [Abstract]
Costs and estimated earnings in excess of billings on uncompleted contracts	$ 23,785	$ 17,437
Billings in excess of costs and estimated earnings on uncompleted contracts (included in Other current liabilities)	(618)	(263)
Costs and estimated earnings on uncompleted contracts	$ 23,167	$ 17,174

Concentration of Credit Risk (Narrative) (Details) - customer	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Concentration Risk [Line Items]
Number of significant customers	8	8
Accounts Receivable [Member]
Concentration Risk [Line Items]
Number of significant customers		5
Concentration risk percentage of accounts receivable	67.50%	66.90%

Concentration of Credit Risk (Summary of Significant Customers and Percentage of Total Revenue for Specified Time Periods Derived from Such Customers) (Details) - Revenue [Member]	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AT&T [Member]
Concentration Risk [Line Items]
Concentration risk percentage	24.00%	25.00%	25.70%
Sprint [Member]
Concentration Risk [Line Items]
Concentration risk percentage	17.90%	15.10%	16.10%
T-Mobile [Member]
Concentration Risk [Line Items]
Concentration risk percentage	16.40%	16.50%	17.00%
Verizon Wireless [Member]
Concentration Risk [Line Items]
Concentration risk percentage	14.70%	15.20%	15.20%
Domestic Site Leasing [Member] \| AT&T [Member]
Concentration Risk [Line Items]
Concentration risk percentage	31.90%	32.70%	32.70%
Domestic Site Leasing [Member] \| Sprint [Member]
Concentration Risk [Line Items]
Concentration risk percentage	19.60%	18.90%	19.80%
Domestic Site Leasing [Member] \| T-Mobile [Member]
Concentration Risk [Line Items]
Concentration risk percentage	20.30%	19.70%	19.60%
Domestic Site Leasing [Member] \| Verizon Wireless [Member]
Concentration Risk [Line Items]
Concentration risk percentage	19.00%	19.00%	18.20%
International Site Leasing [Member] \| Oi S.A. [Member]
Concentration Risk [Line Items]
Concentration risk percentage	35.50%	42.20%	43.90%
International Site Leasing [Member] \| Telefonica [Member]
Concentration Risk [Line Items]
Concentration risk percentage	26.70%	25.70%	26.40%
International Site Leasing [Member] \| Claro [Member]
Concentration Risk [Line Items]
Concentration risk percentage	11.40%	10.00%	9.40%
Site Development [Member]
Concentration Risk [Line Items]
Concentration risk percentage	7.00%
Site Development [Member] \| Sprint [Member]
Concentration Risk [Line Items]
Concentration risk percentage	47.10%	12.90%	11.70%
Site Development [Member] \| T-Mobile [Member]
Concentration Risk [Line Items]
Concentration risk percentage	16.40%	26.90%	28.40%
Site Development [Member] \| Verizon Wireless [Member]
Concentration Risk [Line Items]
Concentration risk percentage	6.40%	12.80%	16.50%
Site Development [Member] \| Nokia, Inc. [Member]
Concentration Risk [Line Items]
Concentration risk percentage	3.20%	10.10%	7.10%

Earnings Per Share (Narrative) (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from earnings per share calculation	0.8	1.0	2.2

Earnings Per Share (Weighted-Average Shares of Common Stock Outstanding used in Calculation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net income	$ 57,152	$ 16,144	$ (57,392)	$ 31,547	$ 7,660	$ 49,161	$ 9,233	$ 37,600	$ 47,451	$ 103,654	$ 76,238
Basic weighted-average shares outstanding									114,909	119,860	124,448
Dilutive impact of stock options and restricted shares									1,606	1,162	696
Diluted weighted-average shares outstanding									116,515	121,022	125,144
Net income per common share:
Basic									$ 0.41	$ 0.86	$ 0.61
Diluted									$ 0.41	$ 0.86	$ 0.61

- Definition

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

+ References + Details

- Definition

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

+ References + Details

Debt (Senior Credit Agreement) (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Apr. 11, 2018	Mar. 31, 2018
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,250,000,000	$ 1,250,000,000	$ 1,000,000,000
Revolving credit facility, maturity date	Apr. 11, 2023
2018 Term Loan [Member]
Line of Credit Facility [Line Items]
Debt instrument, face amount		$ 2,400,000,000

Debt (Terms of The Senior Credit Agreement) (Narrative) (Details) - Senior Credit Agreement [Member]	12 Months Ended
	Dec. 31, 2018 item
Debt Instrument [Line Items]
Debt to annualized borrower EBITDA ratio	6.5
Debt and net hedge exposure to annualized borrower EBITDA	6.5
Consecutive trading days	30
Annualized borrower EBITDA to annualized cash interest expense	2.0

Debt (Revolving Credit Facility under the Senior Credit Agreement) (Narrative) (Details) - USD ($)		1 Months Ended	12 Months Ended
	Oct. 13, 2017	Jan. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Feb. 28, 2019	Apr. 11, 2018	Mar. 31, 2018
Line of Credit Facility [Line Items]
Repayments of revolving credit facility			$ 835,000,000	$ 875,000,000	$ 190,000,000
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			$ 1,250,000,000				$ 1,250,000,000	$ 1,000,000,000
Line of credit facility, commitment fee			0.25%
Revolving credit facility, maturity date			Apr. 11, 2023
Borrowings on the revolving credit facility			$ 1,100,000
Line of credit facility, outstanding			325,000,000
Repayments of revolving credit facility	$ 460,000,000		$ 835,000,000
Revolving credit facility, effective interest rate			4.38%
Revolving Credit Facility [Member] \| Subsequent Event [Member]
Line of Credit Facility [Line Items]
Line of credit facility, outstanding						$ 205,000,000
Repayments of revolving credit facility		$ 120,000,000
Minimum [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate			1.125%
Line of credit facility, commitment fee			0.20%
Minimum [Member] \| Revolving Credit Facility [Member] \| Eurodollar [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate			1.125%
Minimum [Member] \| Revolving Credit Facility [Member] \| Base Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate			0.125%
Maximum [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate			1.75%
Line of credit facility, commitment fee			0.25%
Maximum [Member] \| Revolving Credit Facility [Member] \| Eurodollar [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate			1.75%
Maximum [Member] \| Revolving Credit Facility [Member] \| Base Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate			0.75%

Debt (Term Loans under the Senior Credit Agreement) (Narrative) (Details) - USD ($)			3 Months Ended	12 Months Ended
	Feb. 01, 2019	Apr. 11, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Debt instrument, principal balance				$ 10,028,000,000	$ 9,405,000,000
Repayment of term loans				1,947,000,000	20,000,000	$ 20,000,000
2014 Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 1,500,000,000
Debt instrument, maturity date				Mar. 24, 2021
Percentage of par value price for issuance of term loan				99.75%
Quarterly payments				$ 3,800,000
Debt instrument, principal balance					1,447,500,000
Financing fees				14,100,000
Repayment of term loans		$ 1,443,800,000	$ 3,800,000
Write-off of deferred financing fees		5,800,000
Discount related to debt		1,700,000
2015 Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 500,000,000
Debt instrument, maturity date				Jun. 10, 2022
Percentage of par value price for issuance of term loan				99.00%
Quarterly payments				$ 1,300,000
Debt instrument, principal balance					$ 487,500,000
Financing fees				$ 5,500,000
Repayment of term loans		486,300,000	$ 1,300,000
Write-off of deferred financing fees		3,200,000
Discount related to debt		3,100,000
2018 Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 2,400,000,000
Debt instrument, maturity date		Apr. 11, 2025		Apr. 11, 2025
Percentage of par value price for issuance of term loan		99.75%
Quarterly payments				$ 6,000,000
Accruing interest rate during the period				4.53%
Debt instrument, principal balance				$ 2,388,000,000
Financing fees		$ 16,800,000
Repayment of term loans				$ 12,000,000
2014 and 2015 Term Loans [Member]
Debt Instrument [Line Items]
Repayment of term loans		$ 1,930,000,000
Base Rate [Member] \| 2014 Term Loan [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate				1.25%
Rate floor				0.00%
Base Rate [Member] \| 2015 Term Loan [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate				1.25%
Rate floor				0.00%
Base Rate [Member] \| 2018 Term Loan [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate		1.00%
Rate floor		0.00%
Eurodollar [Member] \| 2014 Term Loan [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate				2.25%
Rate floor				0.00%
Eurodollar [Member] \| 2015 Term Loan [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate				2.25%
Rate floor				0.00%
Eurodollar [Member] \| 2018 Term Loan [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate		2.00%
Rate floor		0.00%
Subsequent Event [Member] \| 2018 Term Loan [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Accruing interest rate during the period	4.495%
Loan period	4 years
Notional amount	$ 1,200,000,000
Subsequent Event [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| 2018 Term Loan [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate	2.00%

Debt (Secured Tower Revenue Securities) (Narrative) (Details)									12 Months Ended
	Mar. 09, 2018 USD ($)	Apr. 17, 2017 USD ($)	Jul. 15, 2016 USD ($)	Jul. 07, 2016 USD ($)	Oct. 14, 2015 USD ($)	Oct. 15, 2014 USD ($)	Apr. 18, 2013 USD ($)	Aug. 09, 2012 USD ($)	Dec. 31, 2018 USD ($) site	Dec. 31, 2017 USD ($)	Apr. 16, 2010 USD ($)
Debt Instrument [Line Items]
Debt instrument, principal balance									$ 10,028,000,000	$ 9,405,000,000
Tower Securities [Member]
Debt Instrument [Line Items]
Aggregate number of tower sites owned by Borrowers \| site									10,426
Property management fee percentage									4.50%
U.S. Treasury rate term									10 years
Interest added to Treasury rate and credit-based spread for non-compliance									5.00%
2010-2C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount											$ 550,000,000
Debt instrument, interest rate, stated percentage											5.101%
Repayment date of debt instrument									Apr. 11, 2017
Debt instrument, maturity date									Apr. 09, 2042
Financing fees											$ 8,100,000
Write-off of deferred financing fees			$ 1,000,000
2012 Tower Securities [Member]
Debt Instrument [Line Items]
No prepayment consideration period									12 months
2012-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount								$ 610,000,000
Debt instrument, interest rate, stated percentage								2.933%
Repayment date of debt instrument								Dec. 11, 2017
Debt instrument, maturity date								Dec. 09, 2042
Write-off of deferred financing fees		$ 2,000,000
Repayments of long-term debt		610,000,000
2013 Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount							$ 1,330,000,000
Financing fees							$ 25,500,000
Debt instrument, weighted average interest rate							3.218%
2013-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount							$ 425,000,000
Debt instrument, interest rate, stated percentage							2.24%
Repayment date of debt instrument							Apr. 10, 2018
Debt instrument, maturity date							Apr. 09, 2043		Apr. 10, 2018
Repayments of long-term debt	$ 425,000,000
Debt instrument, principal balance										425,000,000
2013-2C Tower Securities [Member]
Debt Instrument [Line Items]
No prepayment consideration period									18 months
Debt instrument, face amount							$ 575,000,000
Debt instrument, interest rate, stated percentage							3.722%
Repayment date of debt instrument							Apr. 11, 2023
Debt instrument, maturity date							Apr. 09, 2048		Apr. 11, 2023
Debt instrument, principal balance									$ 575,000,000	575,000,000
2013-1D Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount							$ 330,000,000
Debt instrument, interest rate, stated percentage							3.598%
Repayment date of debt instrument							Apr. 10, 2018
Debt instrument, maturity date							Apr. 09, 2043		Apr. 10, 2018
Repayments of long-term debt	330,000,000
Debt instrument, principal balance										330,000,000
2014 Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 1,540,000,000
Financing fees						$ 22,500,000
Debt instrument, weighted average interest rate						3.289%
2014-1C Tower Securities [Member]
Debt Instrument [Line Items]
No prepayment consideration period									12 months
Debt instrument, face amount						$ 920,000,000
Debt instrument, interest rate, stated percentage						2.898%
Repayment date of debt instrument						Oct. 08, 2019
Debt instrument, maturity date						Oct. 11, 2044			Oct. 08, 2019
Debt instrument, principal balance									$ 920,000,000	920,000,000
2014-2C Tower Securities [Member]
Debt Instrument [Line Items]
No prepayment consideration period									18 months
Debt instrument, face amount						$ 620,000,000
Debt instrument, interest rate, stated percentage						3.869%
Repayment date of debt instrument						Oct. 08, 2024
Debt instrument, maturity date						Oct. 08, 2049			Oct. 08, 2024
Debt instrument, principal balance									$ 620,000,000	620,000,000
2015-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount					$ 500,000,000
Debt instrument, interest rate, stated percentage					3.156%
Repayment date of debt instrument					Oct. 08, 2020
Debt instrument, maturity date					Oct. 10, 2045				Oct. 08, 2020
Financing fees					$ 11,200,000
Debt service coverage ratio									2
Debt instrument, principal balance									$ 500,000,000	500,000,000
2016-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 700,000,000
Debt instrument, interest rate, stated percentage				2.877%
Repayment date of debt instrument				Jul. 09, 2021
Debt instrument, maturity date				Jul. 10, 2046					Jul. 09, 2021
Financing fees				$ 9,500,000
Debt instrument, principal balance									$ 700,000,000	700,000,000
2017-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 760,000,000
Debt instrument, interest rate, stated percentage		3.168%
Repayment date of debt instrument		Apr. 11, 2022
Debt instrument, maturity date		Apr. 09, 2047							Apr. 11, 2022
Financing fees		$ 10,200,000
Debt instrument, principal balance									$ 760,000,000	$ 760,000,000
2017-1R Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 40,000,000
Debt instrument, interest rate, stated percentage		4.459%
Repayment date of debt instrument		Apr. 11, 2022
Debt instrument, maturity date		Apr. 09, 2047
2018-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 640,000,000
Debt instrument, interest rate, stated percentage	3.448%
Repayment date of debt instrument	Mar. 09, 2023
Debt instrument, maturity date	Mar. 09, 2048								Mar. 09, 2023
Financing fees	$ 8,500,000
Debt instrument, principal balance									$ 640,000,000
2018-1R Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 33,700,000
Debt instrument, interest rate, stated percentage	4.949%
Repayment date of debt instrument	Mar. 09, 2023
Debt instrument, maturity date	Mar. 09, 2048
Mortgage Loan [Member]
Debt Instrument [Line Items]
Debt instrument, increase	$ 673,700,000
Debt instrument, decrease after giving effect to prepayment of loan components	81,300,000
Debt instrument, increase in outstanding principle amount	640,000,000
Debt instrument, principal balance	$ 4,700,000,000
Minimum [Member] \| Tower Securities [Member]
Debt Instrument [Line Items]
Additional interest rate for non-compliance									5.00%
Excess Cash Flow Reserve [Member] \| Minimum [Member] \| Tower Securities [Member]
Debt Instrument [Line Items]
Debt service coverage ratio									1.30
Amortization Period Prepay [Member] \| Maximum [Member] \| Tower Securities [Member]
Debt Instrument [Line Items]
Debt service coverage ratio									1.15

Debt (Senior Notes) (Narrative) (Details) $ in Thousands						1 Months Ended	12 Months Ended
Debt (Senior Notes) (Narrative) (Details) $ in Thousands	Oct. 13, 2017 USD ($)	Oct. 03, 2016 USD ($)	Oct. 01, 2016 USD ($)	Aug. 15, 2016 USD ($)	Jul. 01, 2014 USD ($)	Jan. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 28, 2012 USD ($)	Jul. 13, 2012 USD ($)
Debt Instrument [Line Items]
Repayments of revolving credit facility							$ 835,000	$ 875,000	$ 190,000
5.75% Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes											$ 800,000
Debt instrument, maturity date							Jul. 15, 2020
Debt instrument, interest rate, stated percentage							5.75%		5.75%		5.75%
Financing fees											$ 14,000
Repayments of unsecured debt				$ 800,000
Debt call premium				25,800
Write-off of deferred financing fees				7,700
5.75% Senior Notes [Member] \| Telecommunications [Member]
Debt Instrument [Line Items]
Ownership interest							100.00%
5.625% Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes										$ 500,000
Debt instrument, maturity date							Oct. 01, 2019
Debt instrument, interest rate, stated percentage							5.625%		5.625%	5.625%
Interest payable dates							April 1 and October 1
Accrued interest		$ 14,100
Financing fees										$ 8,600
Repayments of unsecured debt		500,000		250,000
Debt call premium		$ 14,100
Write-off of deferred financing fees			$ 4,100
2014 Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes					$ 750,000
Debt instrument, maturity date							Jul. 15, 2022
Debt instrument, interest rate, stated percentage					4.875%
Percentage of face value price for issuance of senior notes					99.178%
Interest payable dates							January 15 and July 15
Financing fees					$ 11,600
2014 Senior Notes [Member] \| Redemption, Period Three [Member]
Debt Instrument [Line Items]
Redemption price, percentage							101.219%
2014 Senior Notes [Member] \| Redemption, Period Four [Member]
Debt Instrument [Line Items]
Redemption price, percentage							100.00%
2016 Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes				$ 1,100,000
Debt instrument, maturity date							Sep. 01, 2024
Debt instrument, interest rate, stated percentage				4.875%
Percentage of face value price for issuance of senior notes				99.178%
Interest payable dates							March 1 and September 1
Financing fees				$ 12,800
Redemption price, percentage							104.875%
Aggregate redemption price, percentage							35.00%
2016 Senior Notes [Member] \| Redemption, Period One [Member]
Debt Instrument [Line Items]
Redemption price, percentage							103.656%
2016 Senior Notes [Member] \| Redemption, Period Two [Member]
Debt Instrument [Line Items]
Redemption price, percentage							102.438%
2016 Senior Notes [Member] \| Redemption, Period Three [Member]
Debt Instrument [Line Items]
Redemption price, percentage							101.219%
2016 Senior Notes [Member] \| Redemption, Period Four [Member]
Debt Instrument [Line Items]
Redemption price, percentage							100.00%
2017 Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes	$ 750,000
Debt instrument, maturity date	Oct. 01, 2022						Oct. 01, 2022
Debt instrument, interest rate, stated percentage	4.00%
Interest payable dates							April 1 and October 1
Financing fees	$ 8,900
Redemption price, percentage							104.00%
Aggregate redemption price, percentage							35.00%
2017 Senior Notes [Member] \| Redemption, Period Two [Member]
Debt Instrument [Line Items]
Redemption price, percentage							102.00%
2017 Senior Notes [Member] \| Redemption, Period Three [Member]
Debt Instrument [Line Items]
Redemption price, percentage							100.00%
2017 Senior Notes [Member] \| Redemption, Period Four [Member]
Debt Instrument [Line Items]
Redemption price, percentage							101.00%
Senior Notes [Member]
Debt Instrument [Line Items]
Ratio of indebtedness to annualized consolidated adjusted EBITDA							9.5
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date							Apr. 11, 2023
Repayments of revolving credit facility	$ 460,000						$ 835,000
Revolving Credit Facility [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Repayments of revolving credit facility						$ 120,000

Debt (Schedule of Principal Values, Fair Values, and Carrying Values of Debt) (Details) - USD ($) $ in Thousands									12 Months Ended
	Apr. 11, 2018	Mar. 09, 2018	Oct. 13, 2017	Apr. 17, 2017	Jul. 07, 2016	Oct. 14, 2015	Oct. 15, 2014	Apr. 18, 2013	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Principal Balance									$ 10,028,000	$ 9,405,000
Fair Value									9,736,246	9,436,290
Carrying Value									9,938,553	9,310,686
Less: current maturities of long-term debt									(941,728)	(20,000)
Total long-term debt, net of current maturities									$ 8,996,825	9,290,686
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date									Apr. 11, 2023
Principal Balance									$ 325,000	40,000
Fair Value									325,000	40,000
Carrying Value									$ 325,000	40,000
2014 Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date									Jul. 15, 2022
Principal Balance									$ 750,000	750,000
Fair Value									735,000	770,625
Carrying Value									$ 741,273	739,079
2016 Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date									Sep. 01, 2024
Principal Balance									$ 1,100,000	1,100,000
Fair Value									1,034,000	1,127,500
Carrying Value									$ 1,083,689	1,081,262
2017 Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date			Oct. 01, 2022						Oct. 01, 2022
Principal Balance									$ 750,000	750,000
Fair Value									712,500	750,938
Carrying Value									$ 743,099	741,437
2013-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date								Apr. 09, 2043	Apr. 10, 2018
Principal Balance										425,000
Fair Value										423,853
Carrying Value										424,482
2013-2C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date								Apr. 09, 2048	Apr. 11, 2023
Principal Balance									$ 575,000	575,000
Fair Value									569,164	578,433
Carrying Value									$ 569,715	568,609
2013-1D Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date								Apr. 09, 2043	Apr. 10, 2018
Principal Balance										330,000
Fair Value										330,145
Carrying Value										329,585
2014-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date							Oct. 11, 2044		Oct. 08, 2019
Principal Balance									$ 920,000	920,000
Fair Value									914,241	915,216
Carrying Value									$ 917,728	914,929
2014-2C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date							Oct. 08, 2049		Oct. 08, 2024
Principal Balance									$ 620,000	620,000
Fair Value									609,665	620,942
Carrying Value									$ 614,315	613,461
2015-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date						Oct. 10, 2045			Oct. 08, 2020
Principal Balance									$ 500,000	500,000
Fair Value									496,640	496,840
Carrying Value									$ 495,737	493,474
2016-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date					Jul. 10, 2046				Jul. 09, 2021
Principal Balance									$ 700,000	700,000
Fair Value									691,432	691,166
Carrying Value									$ 694,994	693,118
2017-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Apr. 09, 2047					Apr. 11, 2022
Principal Balance									$ 760,000	760,000
Fair Value									744,496	751,404
Carrying Value									$ 753,028	751,076
2018-1C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date		Mar. 09, 2048							Mar. 09, 2023
Principal Balance									$ 640,000
Fair Value									641,478
Carrying Value									$ 632,725
2014 Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date									Mar. 24, 2021
Principal Balance										1,447,500
Fair Value										1,451,119
Carrying Value										1,439,373
2015 Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date									Jun. 10, 2022
Principal Balance										487,500
Fair Value										488,109
Carrying Value										$ 480,801
2018 Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Apr. 11, 2025								Apr. 11, 2025
Principal Balance									$ 2,388,000
Fair Value									2,262,630
Carrying Value									$ 2,367,250

Debt (Schedule of Future Principal Payment Obligations) (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Debt [Abstract]
2019	$ 944,000
2020	524,000
2021	724,000
2022	2,284,000
2023	$ 1,564,000

Debt (Schedule of Cash and Non-Cash Interest Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 09, 2018	Oct. 13, 2017	Apr. 17, 2017	Aug. 15, 2016	Jul. 07, 2016	Oct. 14, 2015	Jul. 01, 2014	Sep. 28, 2012	Jul. 13, 2012	Apr. 16, 2010
Debt Instrument [Line Items]
Cash Interest	$ 376,217	$ 323,749	$ 329,171
Non-cash Interest	2,640	2,879	2,203
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Cash Interest	$ 7,411	8,046	4,167
5.625% Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest			$ 21,094
Debt instrument, interest rate, stated percentage	5.625%		5.625%								5.625%
5.75% Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest			$ 28,494
Debt instrument, interest rate, stated percentage	5.75%		5.75%									5.75%
2014 Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest	$ 36,563	36,563	$ 36,563
Non-cash Interest	761	724	689
Debt instrument, interest rate, stated percentage										4.875%
2016 Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest	53,625	53,625	20,258
Non-cash Interest	1,003	954	348
Debt instrument, interest rate, stated percentage							4.875%
2017 Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest	30,000	6,500
Debt instrument, interest rate, stated percentage					4.00%
2010-2C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest			15,213
Debt instrument, interest rate, stated percentage													5.101%
2012 Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest		5,330	18,107
2013 Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	25,654	43,217	43,217
2014 Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	51,138	51,138	51,138
2015-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	15,939	15,939	15,939
Debt instrument, interest rate, stated percentage									3.156%
2016-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	20,361	20,361	9,898
Debt instrument, interest rate, stated percentage								2.877%
2017-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	24,354	17,182
Debt instrument, interest rate, stated percentage						3.168%
2018-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	18,072
Debt instrument, interest rate, stated percentage				3.448%
2014 Term Loan [Member]
Debt Instrument [Line Items]
Cash Interest	15,550	49,414	48,962
Non-cash Interest	146	525	510
2015 Term Loan [Member]
Debt Instrument [Line Items]
Cash Interest	5,237	16,641	16,487
Non-cash Interest	187	676	656
2018 Term Loan [Member]
Debt Instrument [Line Items]
Cash Interest	72,648
Non-cash Interest	543
Capitalized Interest And Other [Member]
Debt Instrument [Line Items]
Cash Interest	$ (335)	$ (207)	$ (366)

Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Feb. 28, 2019	Feb. 16, 2018	Jan. 12, 2017	Jun. 04, 2015	May 20, 2010	Dec. 31, 2007
Class of Stock [Line Items]
Shares registered	400,000,000	400,000,000
Common stock, shares issued	112,433,000	116,446,000
Class A Common Stock [Member]
Class of Stock [Line Items]
Stock repurchased, shares		5,800,000
Shares registered									4,000,000
Shares reclassified as authorized and unissued	1,200,000
Stock Repurchase Program One [Member] \| Class A Common Stock [Member]
Class of Stock [Line Items]
Stock repurchase program, authorized							$ 1,000.0
Stock Repurchase Program Two [Member] \| Class A Common Stock [Member]
Class of Stock [Line Items]
Stock repurchase program, authorized							$ 1,000.0
Stock repurchased, shares		42,163	5,300,000
Stock repurchased, value		$ 4.4	$ 545.7
Weighted average price per share		$ 104.81	$ 102.14
Stock Repurchase Program Three [Member] \| Class A Common Stock [Member]
Class of Stock [Line Items]
Stock repurchase program, authorized						$ 1,000.0
Stock repurchased, value		$ 850.0
Weighted average price per share		$ 146.17
Stock Repurchase Program Four [Member] \| Class A Common Stock [Member]
Class of Stock [Line Items]
Stock repurchase program, authorized					$ 1.0
Stock repurchased, shares	5,000,000
Stock repurchased, value	$ 795.5
Weighted average price per share	$ 159.87
Stock Repurchase Program Four [Member] \| Class A Common Stock [Member] \| Subsequent Event [Member]
Class of Stock [Line Items]
Stock repurchase program, remaining authorization				$ 204.5
2010 Plan [Member] \| Class A Common Stock [Member]
Class of Stock [Line Items]
Maximum issuance of shares	15,000,000							15,000,000
Common stock, shares issued	0	487,963	0

Stock-Based Compensation (Narrative) (Details) - USD ($)		3 Months Ended		12 Months Ended
	May 23, 2018	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	May 20, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeiture period once emplyment has ended				90 days
Weighted-average fair value of options granted				$ 33.01	$ 23.88	$ 19.19
Total intrinsic value for options exercised				$ 78,000,000	$ 37,200,000	$ 36,800,000
Cash received from option exercises				74,700,000	56,500,000	27,400,000
Tax benefit realized from stock option exercises				$ 0	0	0
Share price				$ 161.89
Total fair value of shares vested				$ 24,000,000	21,400,000	18,500,000
Non-cash compensation expense				42,327,000	38,249,000	32,915,000
Non-cash compensation capitalized to fixed and intangible assets				800,000	600,000	500,000
Scenario, Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Accelerated compensation cost		$ 7,300,000	$ 11,200,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to unvested stock options				$ 43,300,000
Weighted average period to recognize cost				2 years 6 months
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period to recognize cost				2 years 7 months 6 days
Total unrecognized compensation expense related to unvested restricted stock				$ 28,100,000
2010 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum issuance of granted				7,500,000
Shares remaining available for future issuance under the plan				6,500,000
2010 Plan [Member] \| Class A Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum issuance of shares				15,000,000			15,000,000
Shares remaining available for future issuance under the plan				6,500,000
2008 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares remaining available for future issuance under the plan				289,948
Percentage of purchase plan price per share equal to the fair market value				85.00%
Non-cash compensation expense				$ 600,000	$ 600,000	$ 500,000
2008 Plan [Member] \| Class A Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum issuance of shares				500,000
Class A common stock issued under the purchase plan				16,798	28,232
Cash proceeds from issuance of shares under the purchase plan				$ 2,300,000	$ 3,300,000
2018 Plan [Member] \| Class A Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares remaining available for future issuance under the plan	300,000
Percentage of purchase plan price per share equal to the fair market value	85.00%
Class A common stock issued under the purchase plan				10,052
Cash proceeds from issuance of shares under the purchase plan				$ 1,400,000
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life of options and restricted stock units				7 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life of options and restricted stock units				10 years

Stock-Based Compensation (Schedule of Assumptions used to Estimate Fair Value of Stock Options) (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock-Based Compensation [Abstract]
Risk free interest rate, Minimum	2.57%	1.70%	1.11%
Risk free interest rate, Maximum	2.92%	1.97%	1.43%
Dividend yield	0.70%	0.00%	0.00%
Expected volatility	21.60%	20.00%	20.00%
Expected lives	4 years 7 months 6 days	4 years 7 months 6 days	4 years 8 months 12 days

Stock-Based Compensation (Summary of Stock Option Activity) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock-Based Compensation [Abstract]
Number of Shares, Outstanding at December 31,	4,842	4,447	3,794
Number of Shares, Granted	941	1,171	1,357
Number of Shares, Exercised	(926)	(709)	(603)
Number of Shares, Forfeited/canceled	(41)	(67)	(101)
Number of Shares,Outstanding at December 31,	4,816	4,842	4,447
Number of Shares, Exercisable at December 31,	2,162
Number of Shares, Unvested at December 31,	2,654
Weighted-Average Exercise Price Per Share, Outstanding at December 31,	$ 100.12	$ 93.09	$ 84.66
Weighted-Average Exercise Price Per Share, Granted	156.55	115.41	96.64
Weighted-Average Exercise Price Per Share, Exercised	81.73	80.73	46.03
Weighted-Average Exercise Price Per Share, Forfeited/canceled	123.98	105.81	105.37
Weighted-Average Exercise Price Per Share, Outstanding at December 31,	114.48	$ 100.12	$ 93.09
Weighted-Average Exercise Price Per Share, Exercisable at December 31,	100.15
Weighted-Average Exercise Price Per Share, Unvested at December 31,	$ 126.17
Weighted-Average Remaining Contractual Life (in years), Outstanding at December 31,	4 years 2 months 12 days
Weighted-Average Remaining Contractual Life (in years), Exercisable at December 31,	3 years
Weighted-Average Remaining Contractual Life (in years), Unvested at December 31,	5 years 1 month 6 days
Aggregate Intrinsic Value, Outstanding at December 31,	$ 228,248
Aggregate Intrinsic Value, Exercisable at December 31,	133,490
Aggregate Intrinsic Value, Unvested at December 31,	$ 94,758

Stock-Based Compensation (Additional Information Regarding Options Outstanding And Exercisable) (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number of Shares \| shares	4,816
Options Exercisable, Number of Shares \| shares	2,162
$0.00 - $90.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit	$ 0.00
Exercise price range, upper limit	$ 90.00
Options Outstanding, Number of Shares \| shares	406
Options Outstanding, Weighted Average Remaining Contractual Life	1 year
Options Outstanding, Weighted Average Exercise Price	$ 68.96
Options Exercisable, Number of Shares \| shares	406
Options Exercisable, Weighted Average Exercise Price	$ 68.96
$90.01 - $110.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit	90.01
Exercise price range, upper limit	$ 110.00
Options Outstanding, Number of Shares \| shares	1,609
Options Outstanding, Weighted Average Remaining Contractual Life	3 years 6 months
Options Outstanding, Weighted Average Exercise Price	$ 96.29
Options Exercisable, Number of Shares \| shares	983
Options Exercisable, Weighted Average Exercise Price	$ 96.08
$110.01- $145.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit	110.01
Exercise price range, upper limit	$ 145.00
Options Outstanding, Number of Shares \| shares	1,871
Options Outstanding, Weighted Average Remaining Contractual Life	4 years 4 months 24 days
Options Outstanding, Weighted Average Exercise Price	$ 119.15
Options Exercisable, Number of Shares \| shares	773
Options Exercisable, Weighted Average Exercise Price	$ 121.69
$145.01 - $175.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit	145.01
Exercise price range, upper limit	$ 175.00
Options Outstanding, Number of Shares \| shares	930
Options Outstanding, Weighted Average Remaining Contractual Life	6 years 2 months 12 days
Options Outstanding, Weighted Average Exercise Price	$ 156.55
Options Exercisable, Weighted Average Exercise Price	$ 0.00

Stock-Based Compensation (Summary of Activity of Options Outstanding not yet Vested) (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock-Based Compensation [Abstract]
Number of Shares, Unvested as of December 31, 2017	2,860
Number of Shares, Granted	941	1,171	1,357
Number of Shares, Vesting during period	(1,104)
Number of Shares, Forfeited/cancelled	(43)
Number of Shares, Unvested as of December 31, 2018	2,654	2,860
Weighted-Average Fair Value Per Share, Unvested as of December 31, 2017	$ 22.08
Weighted-Average Fair Value Per Share, Granted	33.01	$ 23.88	$ 19.19
Weighted-Average Fair Value Per Share, Vesting during period	21.74
Weighted-Average Fair Value Per Share, Forfeited/canceled	26.32
Weighted-Average Fair Value Per Share, Unvested as of December 31, 2018	$ 26.05	$ 22.08

Stock-Based Compensation (Summary of Restricted Stock Unit Activity) (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Stock-Based Compensation [Abstract]
Number of Shares, Outstanding at December 31, \| shares	328
Number of Shares, Granted \| shares	138
Number of Shares, Vested \| shares	(129)
Number of Shares, Forfeited/canceled \| shares	(13)
Number of Shares, Outstanding at December 31, \| shares	324
Weighted-Average Grant Date Fair Value per Share, Outstanding at December 31, \| $ / shares	$ 110.20
Weighted-Average Grant Date Fair Value per Share, Granted \| $ / shares	156.61
Weighted-Average Grant Date Fair Value per Share, Vested \| $ / shares	110.93
Weighted-Average Grant Date Fair Value per Share, Forfeited/canceled \| $ / shares	135.22
Weighted-Average Grant Date Fair Value per Share, Outstanding at December 31, \| $ / shares	$ 128.69

Stock-Based Compensation (Schedule of Non-Cash Compensation Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total cost of non-cash compensation included in loss before provision for income taxes	$ 42,327	$ 38,249	$ 32,915
Amount charged against loss	42,327	38,249	32,915
Cost of Revenues [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total cost of non-cash compensation included in loss before provision for income taxes	1,182	1,013	418
Selling, General And Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total cost of non-cash compensation included in loss before provision for income taxes	$ 41,145	$ 37,236	$ 32,497

Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Income Taxes [Line Items]
Effective income tax rate	21.00%	35.00%	35.00%
Net foreign operating loss carry-forward	$ 85,000
Valuation allowance recognized	50,600	$ 38,800
Net change in valuation allowance	(11,800)	31,400
Deferred Tax Assets, Operating Loss Carryforwards, Domestic	5,600
Net federal operating tax loss carry-forward	863,100,000	857,500
Net state operating tax loss carry-forward	412,200
One-time income inclusion of unremitted earnings as a result of the Tax Act		$ 52,400
Deferred foreign withholding taxes	6,225
Transition tax	$ 49,200
Transition taxable income inclusion period	8 years
Transition tax inclusion	$ 41,300
Transition tax inclusion included in taxable income, period	6 years
Reduction to deferred tax asset and offsetting valuation allowance	$ 12,300
Deferred tax asset offset by valuation allowance	6,000
Real Estate Investment Trust [Member]
Schedule Of Income Taxes [Line Items]
Net federal operating tax loss carry-forward	$ 755,400,000
Minimum [Member]
Schedule Of Income Taxes [Line Items]
Operating loss carry-forward, expiration year	2024
Foreign and state operating tax loss carry forwards expiration date	2020
Maximum [Member]
Schedule Of Income Taxes [Line Items]
Operating loss carry-forward, expiration year	2037

Income Taxes (Income (Loss) Before Provision For Income Taxes From Continuing Operations By Geographic Area) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Abstract]
Domestic	$ 99,203	$ 73,405	$ (28,671)
Foreign	(47,519)	43,486	115,974
Total	$ 51,684	$ 116,891	$ 87,303

Income Taxes (Components of Provision for Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current provision:
State	$ 5,764	$ 5,513	$ 1,535
Foreign	13,756	11,681	8,121
Total current	19,520	17,194	9,656
Deferred provision (benefit) for taxes:
Federal	(9,463)	18,736	170,177
State	(1,412)	(241)	22,992
Foreign	(16,673)	9,155	30,425
Change in valuation allowance	12,261	(31,607)	(222,185)
Total deferred	(15,287)	(3,957)	1,409
Total provision for income taxes	$ 4,233	$ 13,237	$ 11,065

Income Taxes (Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Abstract]
Statutory federal expense	$ 10,854	$ 40,912	$ 30,555
Rate and permanent differences on non-U.S. earnings	3,620	3,690	(4,739)
State and local tax expense	4,824	5,415	3,941
REIT adjustment	(22,241)	(34,346)	205,317
Permanent differences	437	(1,365)	(3,577)
Tax Act impact on deferred taxes	(6,040)	31,547
Other	518	(1,009)	1,753
Valuation allowance	12,261	(31,607)	(222,185)
Total provision for income taxes	$ 4,233	$ 13,237	$ 11,065

Income Taxes (Components of Net Deferred Income Tax Asset and Liability) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Noncurrent deferred tax assets:
Net operating losses	$ 63,622	$ 65,257
Property, equipment and intangible basis differences	4,793	3,038
Accrued liabilities	9,659	11,933
Non-cash compensation	16,641	7,500
Deferred revenue	2,005	2,110
Allowance for doubtful accounts	5,691	5,978
Currency translation	56,604	34,895
Other	2,480	2,698
Valuation allowance	(50,628)	(38,802)
Total noncurrent deferred tax assets, net	110,867	94,607
Noncurrent deferred tax liabilities:
Property, equipment and intangible basis differences	(114,652)	(98,589)
Straight-line rents	(20,469)	(22,740)
Deferred foreign withholding taxes	(6,225)
Deferred lease costs	(2,192)	(2,242)
Other	(123)	(136)
Total noncurrent deferred tax liabilities, net	(32,794)	(29,100)
Other assets [Member]
Noncurrent deferred tax assets:
Total noncurrent deferred tax assets, net	18,330	1,670
Other Long-Term Liabilities [Member]
Noncurrent deferred tax liabilities:
Total noncurrent deferred tax liabilities, net	$ (51,124)	$ (30,770)

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Commitments And Contingencies [Line Items]
Rent expense for operating leases	$ 273.5	$ 266.4	$ 253.7
Contingent rent expense	$ 27.1	$ 26.6	$ 25.0
Non-cancelable Operating Leases [Member]
Schedule Of Commitments And Contingencies [Line Items]
Lease expiration period	Dec. 01, 2152
Non-cancelable Capital Leases [Member]
Schedule Of Commitments And Contingencies [Line Items]
Lease expiration period	Aug. 01, 2022
Minimum [Member]
Schedule Of Commitments And Contingencies [Line Items]
Business acquisitions performance target period	1 year
Maximum [Member]
Schedule Of Commitments And Contingencies [Line Items]
Business acquisitions performance target period	3 years

- Definition

The increases or decreases in lease payments that result from changes occurring after the inception of the lease in the factors (other than the passage of time) on which lease payments are based, except that any escalation of minimum lease payments relating to increases in construction or acquisition cost of the leased property or for increases in some measure of cost or value during the construction or preconstruction period, are excluded from contingent rentals. Contingent rentals also may include amounts for which the triggering events have not yet occurred or the specified targets for which have not yet been achieved (such as sales based percentage rent), but which events are considered probable of occurring or which specified targets are considered probable of being achieved.

+ References + Details

Commitments and Contingencies (Annual Minimum Lease Payments) (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments and Contingencies [Abstract]
Capital Leases, due on 2019	$ 883
Capital Leases, due on 2020	482
Capital Leases, due on 2021	303
Capital Leases, due on 2022	86
Total minimum lease payments	1,754
Less: amount representing interest	(83)
Present value of future payments	1,671
Less: current obligations	(860)
Long-term obligations	811
Operating Leases, due on 2019	237,730
Operating Leases, due on 2020	239,208
Operating Leases, due on 2021	241,090
Operating Leases, due on 2022	242,320
Operating Leases, due on 2023	$ 243,476

Commitments and Contingencies (Annual Minimum Tower Lease Income) (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments and Contingencies [Abstract]
2019	$ 1,529,902
2020	1,326,108
2021	1,075,675
2022	815,219
2023	$ 598,987

Defined Contribution Plan (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan [Abstract]
Condition to participate in defined contribution plan	Employees have the opportunity to participate following completion of three months of employment and must be 21 years of age.
Discretionary matching contribution company percentage	75.00%
Discretionary matching contribution, employee's contribution, maximum	$ 4,000
Company matching contributions	$ 2,100,000	$ 2,000,000	$ 2,000,000

Segment Data (Narrative) (Details) $ in Thousands	12 Months Ended
Segment Data (Narrative) (Details) $ in Thousands	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of business segments \| segment	2
Number of reportable segments \| segment	2
Site leasing	$ 1,740,434	$ 1,623,173	$ 1,538,070
Total assets	7,213,707	7,320,205
Brazil [Member]
Segment Reporting Information [Line Items]
Site leasing	221,500	217,400	$ 178,300
Total assets	$ 1,031,600	$ 1,278,900

Segment Data (Schedule of Segment Reporting Information) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 483,849	$ 467,221	$ 456,322	$ 458,303	$ 443,073	$ 433,945	$ 427,294	$ 423,362	$ 1,865,695	$ 1,727,674	$ 1,633,125
Cost of revenues									468,795	446,312	420,897
Operating profit									1,396,900	1,281,362	1,212,228
Selling, general, and administrative									142,526	130,697	143,349
Acquisition related adjustments and expenses									10,961	12,367	13,140
Asset impairment and decommission costs									27,134	36,697	30,242
Depreciation, amortization and accretion	169,454	167,703	169,558	165,398	162,643	161,907	159,520	159,030	672,113	643,100	638,189
Operating income	150,321	$ 138,006	$ 125,870	$ 129,969	119,081	$ 117,011	$ 114,590	$ 107,819	544,166	458,501	387,308
Other expense (principally interest expense and other expense)									(492,482)	(341,610)	(300,005)
Income before provision for income taxes									51,684	116,891	87,303
Cash capital expenditures									602,680	588,845	418,203
Assets	7,213,707				7,320,205				7,213,707	7,320,205
Provision for doubtful accounts									551	2,909	22,516
Domestic Site Leasing [Member]
Segment Reporting Information [Line Items]
Revenues									1,400,095	1,308,389	1,273,866
Cost of revenues									266,131	260,826	260,941
Operating profit									1,133,964	1,047,563	1,012,925
Selling, general, and administrative									72,879	67,263	72,701
Acquisition related adjustments and expenses									5,268	8,171	6,233
Asset impairment and decommission costs									18,857	29,523	26,073
Depreciation, amortization and accretion									511,823	498,842	509,108
Operating income									525,137	443,764	398,810
Cash capital expenditures									338,610	225,074	310,256
Assets	5,035,826				5,171,190				5,035,826	5,171,190
International Site Leasing [Member]
Segment Reporting Information [Line Items]
Revenues									340,339	314,784	264,204
Cost of revenues									106,165	98,701	81,274
Operating profit									234,174	216,083	182,930
Selling, general, and administrative									27,082	24,320	35,897
Acquisition related adjustments and expenses									5,693	4,196	6,907
Asset impairment and decommission costs									7,932	6,994	1,824
Depreciation, amortization and accretion									151,570	135,155	119,466
Operating income									41,897	45,418	18,836
Cash capital expenditures									258,785	358,691	102,282
Assets	2,042,800				2,028,479				2,042,800	2,028,479
Site Development [Member]
Segment Reporting Information [Line Items]
Revenues									125,261	104,501	95,055
Cost of revenues									96,499	86,785	78,682
Operating profit									28,762	17,716	16,373
Selling, general, and administrative									16,215	15,433	13,039
Asset impairment and decommission costs									345	180
Depreciation, amortization and accretion									2,556	2,580	3,402
Operating income									9,646	(477)	(68)
Cash capital expenditures									1,561	1,221	1,955
Assets	60,775				49,487				60,775	49,487
Not Identified by Segment [Member]
Segment Reporting Information [Line Items]
Selling, general, and administrative									26,350	23,681	21,712
Asset impairment and decommission costs											2,345
Depreciation, amortization and accretion									6,164	6,523	6,213
Operating income									(32,514)	(30,204)	(30,270)
Other expense (principally interest expense and other expense)									(492,482)	(341,610)	(300,005)
Cash capital expenditures									3,724	3,859	$ 3,710
Assets	$ 74,306				$ 71,049				$ 74,306	71,049
Oi S.A. [Member]
Segment Reporting Information [Line Items]
Provision for doubtful accounts										$ 16,498

Quarterly Financial Data (Schedule of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Revenues	$ 483,849	$ 467,221	$ 456,322	$ 458,303	$ 443,073	$ 433,945	$ 427,294	$ 423,362	$ 1,865,695	$ 1,727,674	$ 1,633,125
Operating income	150,321	138,006	125,870	129,969	119,081	117,011	114,590	107,819	544,166	458,501	387,308
Depreciation, accretion, and amortization	(169,454)	(167,703)	(169,558)	(165,398)	(162,643)	(161,907)	(159,520)	(159,030)	(672,113)	(643,100)	(638,189)
Loss from extinguishment of debt, net			(13,798)	(645)			(1,961)		(14,087)	(1,961)	(52,701)
Net income (loss)	$ 57,152	$ 16,144	$ (57,392)	$ 31,547	$ 7,660	$ 49,161	$ 9,233	$ 37,600	$ 47,451	$ 103,654	$ 76,238
Net income per common share - basic	$ 0.50	$ 0.14	$ (0.50)	$ 0.27	$ 0.07	$ 0.41	$ 0.08	$ 0.31	$ 0.41	$ 0.86	$ 0.61
Net income per common share - diluted	$ 0.50	$ 0.14	$ (0.50)	$ 0.27	$ 0.06	$ 0.41	$ 0.08	$ 0.31	$ 0.41	$ 0.86	$ 0.61

Accrued Expenses (Schedule of Accrued Expenses) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued Expenses [Abstract]
Salaries and benefits	$ 16,015	$ 13,506
Real estate and property taxes	7,928	7,125
Non-cash capital expenditures	12,387	12,408
Other	27,335	36,823
Total accrued expenses	$ 63,665	$ 69,862

Schedule III - Schedule of Real Estate and Accumulated Depreciation (Schedule of Real Estate and Accumulated Depreciation) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) site	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Description \| site	29,578
Encumbrances	$ 7,428,000
Gross Amount Carried at Close of Current Period	5,561,005	$ 5,340,858	$ 5,079,660	$ 4,839,874
Accumulated Depreciation at Close of Current Period	$ (2,868,507)	$ (2,627,841)	$ (2,396,587)	$ (2,160,530)
Date of Construction	Various
Date Acquired	Various
Secured debt	$ 7,400,000
Maximum [Member]
Life on Which Depreciation in Latest Income Statement is Computed	20 years
Minimum [Member] \| Real Estate, Gross [Member]
Concentration risk percentage	5.00%

Schedule III - Schedule of Real Estate and Accumulated Depreciation (Reconciliation of Carrying Amount of Real Estate Investments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule III - Schedule of Real Estate and Accumulated Depreciation [Abstract]
Gross amount at beginning	$ 5,340,858	$ 5,079,660	$ 4,839,874
Acquisitions	131,686	112,979	72,456
Construction and related costs on new builds	54,237	70,361	58,143
Augmentation and tower upgrades	49,201	43,288	37,861
Land buyouts and other assets	37,032	41,657	44,574
Tower maintenance	30,048	29,391	28,257
Other			45,829
Total additions	302,204	297,676	287,120
Cost of real estate sold or disposed	(1,083)	(1,027)	(12,842)
Impairment	(17,130)	(34,101)	(34,492)
Other	(63,844)	(1,350)
Total deductions	(82,057)	(36,478)	(47,334)
Balance at end	$ 5,561,005	$ 5,340,858	$ 5,079,660

Schedule III - Schedule of Real Estate and Accumulated Depreciation (Reconciliation of Real Estate Accumulated Depreciation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule III - Schedule of Real Estate and Accumulated Depreciation [Abstract]
Gross amount of accumulated depreciation at beginning	$ (2,627,841)	$ (2,396,587)	$ (2,160,530)
Depreciation	(257,469)	(248,818)	(254,982)
Other	(25)		(5,557)
Total additions	(257,494)	(248,818)	(260,539)
Amount of accumulated depreciation for assets sold or disposed	4,392	17,051	24,482
Other	12,436	513
Total deductions	16,828	17,564	24,482
Balance at end	$ (2,868,507)	$ (2,627,841)	$ (2,396,587)