Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from operating activities
Net income (loss)	$ (1,256,245)	$ 3,110
Adjustments to reconcile net income (loss) to cash flow from operating activities
Depletion, depreciation, and amortization	297,898	289,294
Write-down of oil and natural gas properties	1,852,000	0
Deferred income taxes	(700,508)	1,611
Stock-based compensation	14,967	17,217
Commodity derivatives expense (income)	(34,150)	251,440
Receipt (payment) on settlements of commodity derivatives	272,616	(77,341)
Loss on early extinguishment of debt	0	113,908
Amortization of debt issuance costs and discounts	4,501	6,978
Other, net	(4,019)	(3,402)
Changes in assets and liabilities, net of effects from acquisitions
Accrued production receivable	17,683	(25,236)
Trade and other receivables	57,865	12,921
Other current and long-term assets	(7,770)	(2,989)
Accounts payable and accrued liabilities	(71,892)	(36,178)
Oil and natural gas production payable	(13,217)	(2,033)
Other liabilities	(3,008)	(4,595)
Net cash provided by operating activities	426,721	544,705
Cash flows from investing activities
Oil and natural gas capital expenditures	(276,783)	(451,564)
Acquisitions of oil and natural gas properties	(20,374)	0
CO2 capital expenditures	(15,608)	(29,901)
Pipelines and plants capital expenditures	(20,349)	(34,530)
Purchases of other assets	(3,473)	(3,620)
Net proceeds from sales of oil and natural gas properties and equipment	131	1,736
Other	(56)	977
Net cash used in investing activities	(336,512)	(516,902)
Cash flows from financing activities
Bank repayments	(1,007,000)	(1,315,000)
Bank borrowings	962,000	1,420,000
Repayment of senior subordinated notes	0	(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	(1,632)	(17,551)
Common stock repurchase program	0	(211,356)
Cash dividends paid	(43,528)	(43,461)
Other	(18,789)	(11,889)
Net cash used in financing activities	(108,949)	(27,944)
Net decrease in cash and cash equivalents	(18,740)	(141)
Cash and cash equivalents at beginning of period	23,153	12,187
Cash and cash equivalents at end of period	$ 4,413	$ 12,046