CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 281,998	$ 144,834
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation, depletion and amortization	288,210	425,689
Impairment of oil and gas properties	0	68,555
Deferred income tax expense	131,799	89,731
Loss on sale of assets	14,850	13,498
Exploratory dry hole cost	56,425	2,842
(Gain) loss on derivative instruments	1,628	(46,353)
Net cash received (paid) in settlement of derivative instruments	(20,354)	3,587
Loss on equity method investments	1,009	3,986
Amortization of debt issuance costs	3,521	3,579
Stock-based compensation and other	16,472	26,011
Changes in assets and liabilities:
Accounts receivable, net	(7,345)	29,276
Income taxes	(14,447)	(16,665)
Inventories	(5,326)	(2,100)
Other current assets	104	(896)
Accounts payable and accrued liabilities	32,192	(5,133)
Interest payable	(18,474)	(15,318)
Other assets and liabilities	26,590	(6,076)
Net cash provided by operating activities	788,852	719,047
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(647,503)	(586,813)
Proceeds from sale of assets	675,525	32,711
Investment in equity method investments	(72,866)	(23,382)
Net cash used in investing activities	(44,844)	(577,484)
CASH FLOWS FROM FINANCING ACTIVITIES
Repayments of debt	(237,000)	0
Treasury stock repurchases	(581,725)	(68,255)
Dividends paid	(81,185)	(55,707)
Tax withholdings on vesting of stock awards	(8,068)	(5,929)
Other	0	42
Net cash used in financing activities	(907,978)	(129,849)
Net increase (decrease) in cash and cash equivalents	(163,970)	11,714
Cash and cash equivalents, beginning of period	480,047	498,542
Cash and cash equivalents, end of period	$ 316,077	$ 510,256