Consolidated Statements of Cash Flows - USD ($) shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income	$ (9,702)	$ 95,994
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation, accretion, and amortization	502,659	480,457
Non-cash asset impairment and decommission costs	22,146	22,316
Non-cash compensation expense	32,140	28,894
Amortization of deferred financing fees	15,265	16,603
Loss (gain) on remeasurement of U.S. dollar denominated intercompany loans	113,138	(11,649)
Loss from extinguishment of debt	14,087	1,961
Deferred income tax benefit	(27,925)	(1,220)
Other non-cash items reflected in the Statements of Operations	2,022	237
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable and costs and estimated earnings in excess of billings on uncompleted contracts, net	(4,655)	(11,950)
Prepaid expenses and other assets	(28,061)	(18,168)
Accounts payable and accrued expenses	(2,496)	4,846
Accrued interest	(14,813)	(24,836)
Other liabilities	10,338	7,987
Net cash provided by operating activities	624,143	591,472
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions	(403,835)	(161,007)
Capital expenditures	(104,966)	(106,310)
Purchase of investments	(99,823)	(382)
Proceeds from sale of investments	95,890
Other investing activities	(7,583)	(23,216)
Net cash used in investing activities	(520,317)	(290,915)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings under Revolving Credit Facility	805,000	415,000
Repayments under Revolving Credit Facility	(725,000)	(375,000)
Repayment of Tower Securities	(755,000)	(610,000)
Proceeds from issuance of Tower Securities, net of fees	631,479	749,811
Proceeds from Term Loans, net of fees	2,377,264
Repayment of Term Loans	(1,941,000)	(15,000)
Repurchase and retirement of common stock	(453,539)	(523,370)
Other financing activities	29,607	40,957
Net cash used in financing activities	(31,189)	(317,602)
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	(13,608)	3,537
NET CHANGE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	59,029	(13,508)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH:
Beginning of period	104,295	185,970
End of period	163,324	172,462
Cash paid during the period for:
Interest	293,372	262,257
Income taxes	16,525	11,323
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES:
Assets acquired through capital leases	$ 1,142	$ 254
Common stock issued in connection with acquisitions		63,313