Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities
Net income (loss)	$ (3,500,371)	$ 271,858
Adjustments to reconcile net income (loss) to cash flow from operating activities
Depletion, depreciation, and amortization	419,304	435,854
Write-down of oil and natural gas properties	3,612,600	0
Impairment of goodwill	1,261,512	0
Deferred income taxes	(1,432,572)	168,967
Stock-based compensation	22,637	26,104
Commodity derivatives expense (income)	(126,178)	(825)
Receipt (payment) on settlements of commodity derivatives	433,293	(102,255)
Loss on early extinguishment of debt	0	113,908
Amortization of debt issuance costs and discounts	6,810	10,433
Other, net	(7,457)	(5,037)
Changes in assets and liabilities, net of effects from acquisitions
Accrued production receivable	57,867	565
Trade and other receivables	37,463	(6,885)
Other current and long-term assets	(1,771)	(370)
Accounts payable and accrued liabilities	(53,124)	(7,195)
Oil and natural gas production payable	(26,478)	(17,225)
Other liabilities	(4,138)	(2,800)
Net cash provided by operating activities	699,397	885,097
Cash flows from investing activities
Oil and natural gas capital expenditures	(364,948)	(699,012)
Acquisitions of oil and natural gas properties	(21,171)	(1,684)
CO2 capital expenditures	(21,894)	(38,272)
Pipelines and plants capital expenditures	(25,767)	(47,521)
Purchases of other assets	(5,539)	(6,253)
Net proceeds from sales of oil and natural gas properties and equipment	327	3,011
Other	11,452	808
Net cash used in investing activities	(427,540)	(788,923)
Cash flows from financing activities
Bank repayments	(1,491,000)	(1,827,000)
Bank borrowings	1,306,000	1,897,000
Repayment of senior subordinated notes	(485)	(997,345)
Premium paid on repayment of senior subordinated notes	0	(101,342)
Proceeds from issuance of senior subordinated notes	0	1,250,000
Costs of debt financing	(1,639)	(17,551)
Common stock repurchase program	(2,692)	(211,356)
Cash dividends paid	(65,422)	(65,241)
Other	(27,560)	(16,090)
Net cash used in financing activities	(282,798)	(88,925)
Net increase (decrease) in cash and cash equivalents	(10,941)	7,249
Cash and cash equivalents at beginning of period	23,153	12,187
Cash and cash equivalents at end of period	$ 12,212	$ 19,436