CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net loss	$ (209,722,000)	$ (585,054,000)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, depletion, amortization and impairment	296,919,000	359,882,000
Impairment of goodwill		395,060,000
Dry holes and abandonments	171,000	1,238,000
Deferred income tax benefit	(37,073,000)	(87,219,000)
Stock-based compensation expense	11,825,000	13,495,000
Net gain on asset disposals	(4,052,000)	(2,461,000)
Net gain on insurance reimbursement		(4,172,000)
Writedown of capacity reservation contract		9,207,000
Credit loss expense	0	5,606,000
Restructuring expenses, non-cash		30,886,000
Amortization of debt discount and issuance costs	412,000	447,000
Changes in operating assets and liabilities:
Accounts receivable	(36,438,000)	176,072,000
Income taxes receivable/payable	4,369,000	(2,663,000)
Inventory and other assets	(6,423,000)	16,923,000
Accounts payable	34,465,000	(65,915,000)
Accrued liabilities	(8,785,000)	(37,237,000)
Other liabilities	(1,471,000)	(4,762,000)
Net cash provided by operating activities	44,197,000	219,333,000
Cash flows from investing activities:
Purchases of property and equipment	(56,573,000)	(121,601,000)
Proceeds from disposal of assets and insurance claims	15,145,000	7,265,000
Other	(223,000)
Net cash used in investing activities	(41,651,000)	(114,336,000)
Cash flows from financing activities:
Purchases of treasury stock	(3,522,000)	(20,935,000)
Dividends paid	(7,523,000)	(11,364,000)
Debt issuance costs		145,000
Net cash used in financing activities	(11,045,000)	(32,444,000)
Effect of foreign exchange rate changes on cash	266,000	43,000
Net increase (decrease) in cash and cash equivalents	(8,233,000)	72,596,000
Cash and cash equivalents at beginning of period	224,915,000	174,185,000
Cash and cash equivalents at end of period	216,682,000	246,781,000
Net cash received (paid) during the period for:
Interest, net of capitalized interest of $56 in 2021 and $406 in 2020	(20,604,000)	(21,482,000)
Income taxes	4,226,000	(402,000)
Non-cash investing and financing activities:
Receivable from property and equipment insurance		6,983,000
Net decrease in payables for purchases of property and equipment	(5,232,000)	(36,894,000)
Net decrease in deposits on equipment purchases	$ 117,000	$ 1,390,000