Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Cash flow from operating activities
Net income	$ 271,858	$ 319,605
Adjustments to reconcile net income to cash flow from operating activities
Depletion, depreciation, and amortization	435,854	365,400
Deferred income taxes	168,967	169,634
Stock-based compensation	26,104	23,774
Commodity derivative expense (income)	(825)	46,874
Settlements of commodity derivatives	(102,255)	(662)
Loss on early extinguishment of debt	113,908	44,651
Amortization of debt issuance costs and discounts	10,433	10,581
Other, net	(5,037)	(3,486)
Changes in assets and liabilities, net of effects from acquisitions
Accrued production receivable	565	(34,910)
Trade and other receivables	(6,885)	(756)
Other current and long-term assets	(370)	(1,199)
Accounts payable and accrued liabilities	(7,195)	52,672
Oil and natural gas production payable	(17,225)	31,111
Other liabilities	(2,800)	(11,080)
Net cash provided by operating activities	885,097	1,012,209
Cash flow from investing activities
Oil and natural gas capital expenditures	(699,012)	(688,270)
CO2 capital expenditures	(38,272)	(72,929)
Pipelines and plants capital expenditures	(47,521)	(136,654)
Purchases of other assets	(6,253)	(29,680)
Net proceeds from sales of oil and natural gas properties and equipment	3,011	6,312
Other	(876)	(30,482)
Net cash used in investing activities	(788,923)	(951,703)
Cash flows from financing activities
Bank repayments	(1,827,000)	(1,170,000)
Bank borrowings	1,897,000	780,000
Repayment of senior subordinated notes	(997,345)	(651,270)
Premium paid on repayment of senior subordinated notes	(101,342)	(36,475)
Proceeds from issuance of senior subordinated notes	1,250,000	1,200,000
Costs of debt financing	(17,551)	(20,026)
Common stock repurchase program	(211,356)	(215,197)
Dividends paid	(65,241)	0
Other	(16,090)	(19,501)
Net cash used in financing activities	(88,925)	(132,469)
Net increase (decrease) in cash and cash equivalents	7,249	(71,963)
Cash and cash equivalents at beginning of period	12,187	98,511
Cash and cash equivalents at end of period	$ 19,436	$ 26,548