Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (118,755)	$ (86,114)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, depletion, amortization and accretion	157,657	203,692
Deferred income taxes		(19,300)
Reduction in value of assets	31,381
Right-of-use assets amortization	11,286
Stock based compensation expense	13,507	16,552
Other reconciling items, net	(7,005)	(2,595)
Changes in operating assets and liabilities:
Accounts receivable	67,506	(44,415)
Prepaid expenses	(16,953)	(862)
Inventory and other current assets	(13,680)	(24,854)
Accounts payable	(21,931)	32,852
Accrued expenses	(28,089)	(35,729)
Other, net	(6,094)	188
Net cash provided by operating activities	68,830	39,415
Cash flows from investing activities:
Payments for capital expenditures	(79,136)	(119,841)
Proceeds from sales of assets	84,557	23,297
Net cash provided by (used in) investing activities	5,421	(96,544)
Cash flows from financing activities:
Tax withholdings for vested restricted stock units	(1,677)	(5,183)
Other	651	1,283
Net cash used in financing activities	(1,026)	(3,900)
Effect of exchange rate changes on cash	(102)	(1,311)
Net change in cash, cash equivalents, and restricted cash	73,123	(62,340)
Cash, cash equivalents, and restricted cash at beginning of period	163,748	192,483
Cash, cash equivalents, and restricted cash at end of period	$ 236,871	$ 130,143