Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating activities:
Net loss	$ (282,444)	$ (101,065)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation	263,844	245,534
Loss on impairment of assets		27,225
Loss (gain) on disposition of assets	1,191	(1,066)
Deferred tax provision	(48,323)	(69,109)
Stock-based compensation expense	4,533	4,036
Contract liabilities, net	15,060	(6,589)
Contract assets, net	302	(4,395)
Deferred contract costs, net	49,866	34,901
Other assets, noncurrent	180	823
Other liabilities, noncurrent	(90)	(4,298)
Other	2,408	3,969
Changes in operating assets and liabilities:
Accounts receivable	(27,177)	57,881
Prepaid expenses and other current assets	(128)	4,901
Accounts payable and accrued liabilities	7,115	(11,836)
Taxes payable	(548)	7,844
Net cash (used in) provided by operating activities	(14,211)	188,756
Investing activities:
Capital expenditures	(249,819)	(159,751)
Proceeds from maturities of marketable securities	2,300,000	775,000
Purchase of marketable securities	(1,996,996)	(1,047,453)
Proceeds from disposition of assets, net of disposal costs	16,097	69,533
Net cash provided by (used in) investing activities	69,282	(362,671)
Financing activities:
Other	(12)	(269)
Net cash used in financing activities	(12)	(269)
Net change in cash and cash equivalents	55,059	(174,184)
Cash and cash equivalents, beginning of period	154,073	376,037
Cash and cash equivalents, end of period	$ 209,132	$ 201,853