Condensed Consolidated Statements of Operations (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Revenues and other income
Oil, natural gas, and related product sales	$ 638,188	$ 592,141	$ 1,211,841	$ 1,225,642
CO2 sales and transportation fees	6,562	5,301	13,120	12,096
Interest income and other income	5,334	4,339	8,209	9,159
Total revenues and other income	650,084	601,781	1,233,170	1,246,897
Expenses
Lease operating expenses	220,558	124,511	361,100	262,475
Marketing expenses	13,332	12,218	23,128	23,048
CO2 discovery and operating expenses	3,419	1,062	7,141	7,267
Taxes other than income	44,940	38,812	82,951	82,506
General and administrative	33,382	34,826	75,271	71,433
Interest, net of amounts capitalized of $23,279, $18,475, $44,984, and $37,920, respectively	30,602	41,604	66,636	77,918
Depletion, depreciation, and amortization	126,907	132,289	239,805	253,184
Derivatives expense (income)	(45,501)	(139,109)	(33,572)	(93,834)
Loss on early extinguishment of debt	428	0	44,651	0
Impairment of assets	0	215	0	17,515
Other expenses	10,711	12,552	12,818	23,272
Total expenses	438,778	258,980	879,929	724,784
Income before income taxes	211,306	342,801	353,241	522,113
Income tax provision	81,326	130,936	135,690	196,781
Net income	$ 129,980	$ 211,865	$ 217,551	$ 325,332
Net income per common share - basic	$ 0.35	$ 0.55	$ 0.59	$ 0.84
Net income per common share - diluted	$ 0.35	$ 0.54	$ 0.58	$ 0.83
Weighted average common shares outstanding
Basic	368,850	387,159	369,122	386,764
Diluted	371,969	390,702	372,417	390,823