CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 12,747	$ 225,451
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation, depletion and amortization	328,009	304,981
Deferred income tax expense	7,160	118,453
(Gain) loss on sale of assets	(59)	2,781
Exploratory dry hole cost	178	2,154
(Gain) loss on derivative instruments	(27,304)	2,329
Net cash received (paid) in settlement of derivative instruments	88,730	(15,262)
Amortization of debt issuance costs	2,337	2,252
Stock-based compensation and other	11,602	8,689
Changes in assets and liabilities:
Accounts receivable, net	99,897	9,588
Income taxes	(2,184)	(23,352)
Inventories	(6,397)	5,554
Other current assets	(2,953)	15
Accounts payable and accrued liabilities	(65,023)	(39,084)
Other assets and liabilities	(2,663)	753
Stock-based compensation tax benefit	(5,486)	(20,354)
Net cash provided by operating activities	438,591	584,948
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(645,092)	(617,613)
Acquisitions	(16,300)	0
Proceeds from sale of assets	3,002	(755)
Restricted cash	0	28,094
Investment in equity method investments	(10,114)	(22,230)
Net cash used in investing activities	(668,504)	(612,504)
CASH FLOWS FROM FINANCING ACTIVITIES
Borrowings from debt	642,000	611,000
Repayments of debt	(399,000)	(565,000)
Dividends paid	(16,537)	(16,679)
Stock-based compensation tax benefit	5,486	20,354
Capitalized debt issuance costs	(7,838)	0
Other	79	91
Net cash provided by financing activities	224,190	49,766
Net (decrease) increase in cash and cash equivalents	(5,723)	22,210
Cash and cash equivalents, beginning of period	20,954	23,400
Cash and cash equivalents, end of period	15,231	45,610
Supplemental Cash Flow Information [Abstract]
Change in accrued capital expenditures	$ (134,875)	$ (32,616)