Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net income (loss)	$ (976,177)	$ (4,385,448)	$ 635,491
Adjustments to reconcile net income (loss) to cash flows from operating activities
Depletion, depreciation, and amortization	846,043	531,660	592,972
Write-down of oil and natural gas properties	810,921	4,939,600	0
Impairment of goodwill	0	1,261,512	0
Deferred income taxes	(543,385)	(1,932,179)	429,973
Stock-based compensation	14,995	30,604	30,513
Commodity derivatives expense (income)	127,944	(147,999)	(555,255)
Receipt on settlements of commodity derivatives	84,181	511,699	1,421
Loss (gain) on debt extinguishment	(115,095)	0	113,908
Debt issuance costs and discounts	17,006	9,121	13,476
Other, net	(2,161)	343	6,311
Changes in assets and liabilities, net of effects from acquisitions
Accrued production receivable	(24,290)	81,213	80,285
Trade and other receivables	35,923	67,047	(78,469)
Other current and long-term assets	(8,661)	241	3,174
Accounts payable and accrued liabilities	(34,240)	(55,234)	501
Oil and natural gas production payable	(6,752)	(40,833)	(46,506)
Other liabilities	(7,029)	(7,043)	(4,970)
Net cash provided by operating activities	219,223	864,304	1,222,825
Cash flows from investing activities
Oil and natural gas capital expenditures	(243,027)	(476,398)	(946,846)
Acquisitions of oil and natural gas properties	(1,310)	(21,876)	(8,773)
CO2 capital expenditures	(2,321)	(26,301)	(48,134)
Pipelines and plants capital expenditures	(2,666)	(31,728)	(72,151)
Purchases of other assets	(3,586)	(5,492)	(3,197)
Net proceeds from sales of oil and natural gas properties and equipment	47,725	563	3,453
Other	(232)	11,047	(1,107)
Net cash used in investing activities	(205,417)	(550,185)	(1,076,755)
Cash flows from financing activities
Bank repayments	(1,730,500)	(1,862,000)	(2,609,000)
Bank borrowings	1,856,500	1,642,000	2,664,000
Interest payments on senior secured notes treated as a reduction of debt	(25,835)	0	0
Repayment or repurchases of senior subordinated notes	(76,708)	(485)	(997,345)
Premium paid on repayment of senior subordinated notes	0	0	(101,342)
Proceeds from issuance of senior subordinated notes	0	0	1,250,000
Costs of debt financing	(9,574)	(1,668)	(24,407)
Common stock repurchase program	0	(11,759)	(211,356)
Pipeline financing and capital lease debt repayments	(28,849)	(33,642)	(33,381)
Cash dividends paid	(486)	(65,426)	(87,044)
Other	440	(1,480)	14,771
Net cash used in financing activities	(15,012)	(334,460)	(135,104)
Net increase (decrease) in cash and cash equivalents	(1,206)	(20,341)	10,966
Cash and cash equivalents at beginning of year	2,812	23,153	12,187
Cash and cash equivalents at end of year	$ 1,606	$ 2,812	$ 23,153