Consolidated Statements Of Cash Flows - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 103,654	$ 76,238	$ (175,656)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, accretion, and amortization	643,100	638,189	660,021
Non-cash asset impairment and decommission costs	32,423	25,693	89,406
Non-cash compensation expense	38,249	32,915	28,747
Amortization of deferred financing fees	21,940	21,136	19,154
(Gain) loss on remeasurement of U.S. denominated intercompany loan	8,754	(90,030)	178,854
Gain on sale of cost method investments	0	0	(38,326)
Loss from extinguishment of debt, net	1,961	52,701	783
Provision for doubtful accounts	2,909	22,516	896
Other non-cash items reflected in the Statements of Operations	(4,850)	(1,225)	(5,255)
Changes in operating assets and liabilities, net of acquisitions:
AR and costs and est. earnings in excess of billings on uncompleted contracts, net	(20,893)	(7,270)	15,975
Prepaid expenses and other assets	(16,888)	(40,289)	(62,934)
Accounts payable and accrued expenses	3,555	(10,516)	7,366
Other liabilities	4,556	22,467	3,999
Net cash provided by operating activities	818,470	742,525	723,030
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions	(441,547)	(276,835)	(609,530)
Capital expenditures	(147,044)	(139,982)	(208,707)
Proceeds from sale of investments	231	712	89,728
Other investing activities	(16,747)	(12,130)	(8,556)
Net cash used in investing activities	(605,107)	(428,235)	(737,065)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings under Revolving Credit Facility	525,000	580,000	770,000
Repayments under Revolving Credit Facility	(875,000)	(190,000)	(895,000)
Repayment of Term Loans	(20,000)	(20,000)	(190,000)
Proceeds from issuance of Term Loans, net of fees			489,884
Payments for settlement of common stock warrants			(150,874)
Proceeds from issuance of Senior Notes, net of fees	741,108	1,078,123
Proceeds from issuance of Tower Securities, net of fees	749,764	690,475	489,100
Repayment of Tower Securities	(610,000)	(550,000)
Repurchase and retirement of common stock, inclusive of fees	(854,534)	(545,689)	(450,073)
Other financing activities	49,088	8,394	12,714
Net cash provided by (used in) financing activities	(294,574)	(288,557)	75,751
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	(464)	13,618	(12,993)
NET CHANGE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	(81,675)	39,351	48,723
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH:
Beginning of year	185,970	146,619	97,896
End of year	104,295	185,970	146,619
Cash paid during the period for:
Interest	319,562	338,409	322,396
Income taxes	14,653	9,655	9,431
SUPPLEMENTAL CASH FLOW INFORMATION OF NON-CASH ACTIVITIES:
Assets acquired through capital leases	$ 254	1,386	$ 2,627
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)