CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 200,529	$ 681,070	$ 557,043
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	390,903	405,733	417,479
Deferred income tax expense	71,777	244,418	229,603
Loss on sale of assets	491	1,462	16,327
Exploratory dry hole cost	3,632	2,236	97,741
Gain on derivative instruments	(61,404)	(80,808)	(44,432)
Net cash received (paid) in settlement of derivative instruments	35,218	138,450	(41,631)
Loss (earnings) on equity method investments	59	(80,496)	(1,137)
Distribution of earnings from equity method investments	0	15,725	1,296
Amortization of debt issuance costs	2,961	3,966	4,631
Stock-based compensation and other	40,796	29,009	31,443
Changes in assets and liabilities:
Accounts receivable, net	(5,700)	153,379	(146,921)
Income taxes	123,624	(13,514)	(59,616)
Inventories	(1,981)	(2,856)	(3,927)
Other current assets	34	180	934
Accounts payable and accrued liabilities	(30,040)	(30,176)	30,468
Interest payable	(2,162)	(166)	(7,477)
Other assets and liabilities	9,498	(21,821)	23,079
Net cash provided by operating activities	778,235	1,445,791	1,104,903
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(575,847)	(788,368)	(894,470)
Proceeds from sale of assets	828	2,600	678,350
Investment in equity method investments	(35)	(9,338)	(77,263)
Distribution of investment from equity method investments	0	1,728	0
Proceeds from sale of equity method investments	(9,424)
Proceeds from sale of equity method investments		249,463	0
Net cash used in investing activities	(584,478)	(543,915)	(293,383)
CASH FLOWS FROM FINANCING ACTIVITIES
Borrowings from debt	196,000	95,000	158,000
Repayments of debt	(283,000)	(102,000)	(455,000)
Treasury stock repurchases	0	(519,863)	(872,761)
Dividends paid	(159,390)	(145,515)	(111,369)
Tax withholding on vesting of stock awards	(9,459)	(10,590)	(8,150)
Capitalized debt issuance costs	0	(7,412)	0
Net cash used in financing activities	(255,849)	(690,380)	(1,289,280)
Net (decrease) increase in cash, cash equivalents and restricted cash	(62,092)	211,496	(477,760)
Cash, cash equivalents and restricted cash, beginning of period	213,783	2,287	480,047
Cash, cash equivalents and restricted cash, end of period	$ 151,691	$ 213,783	$ 2,287