Consolidated Statements of Cash Flows - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 147,284	$ 47,451	$ 103,654
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, accretion, and amortization	697,078	672,113	643,100
Non-cash asset impairment and decommission costs	32,241	26,192	32,423
Non-cash compensation expense	73,214	42,327	38,249
Amortization of deferred financing fees	20,358	20,289	21,940
(Gain) loss on remeasurement of U.S. denominated intercompany loans	(13,134)	89,101	8,754
(Recovery) provision for doubtful accounts	(2,141)	551	2,909
Loss from extinguishment of deb, net	235	14,087	1,961
Other non-cash items reflected in the Statements of Operations	19,381	(14,586)	(4,850)
Changes in operating assets and liabilities, net of acquisitions:
AR and costs and est. earnings in excess of billings on uncompleted contracts, net	(12,146)	(29,427)	(20,893)
Prepaid expenses and other assets	878	(38,040)	(16,888)
Operating lease right-of-use assets, net	93,665
Accounts payable and accrued expenses	(5,951)	(3,021)	3,555
Long-term lease liabilities	(87,544)
Other liabilities	6,627	23,581	4,556
Net cash provided by operating activities	970,045	850,618	818,470
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions	(773,957)	(451,829)	(441,547)
Capital expenditures	(154,236)	(149,812)	(147,044)
Purchase of investments	(638,963)	(156,983)	(397)
Proceeds from sale of investments	625,807	150,890	231
Other investing activities	(5,809)	(10,613)	(16,350)
Net cash used in investing activities	(947,158)	(618,347)	(605,107)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings under Revolving Credit Facility	755,000	1,120,000	525,000
Repayments under Revolving Credit Facility	(590,000)	(835,000)	(875,000)
Repayment of Term Loans	(24,000)	(1,947,000)	(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
Proceeds from issuance of Tower Securities, net of fees	1,152,458	631,466	749,764
Repayment of Tower Securities	(920,000)	(755,000)	(610,000)
Repurchase and retirement of common stock	(466,982)	(795,581)	(854,534)
Payment of dividends on common stock	(83,387)
Proceeds from employee stock purchase/stock option plans	116,202	59,880	54,950
Other financing activities	(1,605)	(4,520)	(5,862)
Net cash used in financing activities	(62,314)	(148,537)	(294,574)
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	2,247	(9,729)	(464)
NET CHANGE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	(37,180)	74,005	(81,675)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH:
Beginning of year	178,300	104,295	185,970
End of year	141,120	178,300	104,295
Cash paid during the period for:
Interest	386,615	376,628	319,562
Income taxes	21,598	21,645	14,653
SUPPLEMENTAL CASH FLOW INFORMATION OF NON-CASH ACTIVITIES:
Right-of-use assets obtained in exchange for new operating lease liabilities	175,517
Operating lease modifications and reassessments	52,383
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 3,499	$ 1,039	$ 254
Common stock issued in connection with acquisitions	1,680		63,313
Consolidation of an equity method investment	$ 71,990