CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (28,614)	$ (34,417)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, depletion, amortization and impairment	214,410	209,892
Dry holes and abandonments	21	96
Deferred income tax expense (benefit)	(6,604)	282
Stock-based compensation expense	9,338	9,365
Net gain on asset disposals	(6,545)	(10,410)
Amortization of debt discount and issuance costs	221	170
Changes in operating assets and liabilities:
Accounts receivable	10,929	(16,468)
Income taxes receivable/payable	(14)	19
Inventory and other assets	6,592	2,709
Accounts payable	(17,858)	(22,514)
Accrued expenses	2,871	11,174
Other liabilities	(915)	67
Net cash provided by operating activities	183,832	149,965
Cash flows from investing activities:
Acquisitions, net of cash acquired	(13)	(3,800)
Purchases of property and equipment	(118,341)	(122,921)
Proceeds from disposal of assets and insurance claims	22,054	10,294
Net cash used in investing activities	(96,300)	(116,427)
Cash flows from financing activities:
Purchases of treasury stock	(75,113)	(16,928)
Proceeds from exercise of options		485
Dividends paid	(8,499)	(4,443)
Debt issuance costs		(4,198)
Proceeds from long-term debt		521,194
Proceeds from borrowings under revolving credit facility		79,000
Repayment of borrowings under revolving credit facility		(347,000)
Net cash provided by financing activities	(83,612)	228,110
Effect of foreign exchange rate changes on cash	(48)	(225)
Net increase in cash and cash equivalents	3,872	261,423
Cash and cash equivalents at beginning of period	245,029	42,828
Cash and cash equivalents at end of period	248,901	304,251
Net cash (paid) received during the period for:
Interest, net of capitalized interest of $257 in 2019 and $340 in 2018	(10,689)	(2,206)
Income taxes	(15)	21
Non-cash investing and financing activities:
Receivable from property and equipment insurance		15,000
Net increase (decrease) in payables for purchases of property and equipment	(10,764)	62,488
Net (increase) decrease in deposits on equipment purchases	$ 1,535	$ (2,294)