Condensed Consolidated Statements of Operations (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues and other income
Oil, natural gas, and related product sales	$ 666,803	$ 588,156	$ 1,878,644	$ 1,813,798
CO2 sales and transportation fees	6,739	7,160	19,859	19,256
Interest income and other income	11,293	5,055	19,502	14,214
Total revenues and other income	684,835	600,371	1,918,005	1,847,268
Expenses
Lease operating expenses	180,967	130,485	542,067	392,960
Marketing expenses	13,131	14,728	36,259	37,776
CO2 discovery and operating expenses	4,120	1,176	11,261	8,443
Taxes other than income	49,267	40,012	132,218	122,518
General and administrative expenses	35,969	38,198	111,240	109,631
Interest, net of amounts capitalized of $19,768, $19,437, $64,752, and $57,357, respectively	34,501	37,827	101,137	115,745
Depletion, depreciation, and amortization	125,595	136,935	365,400	390,119
Derivatives expense (income)	80,446	61,631	46,874	(32,203)
Loss on early extinguishment of debt	0	0	44,651	0
Impairment of assets	0	0	0	17,515
Other expenses	1,474	0	14,292	23,272
Total expenses	525,470	460,992	1,405,399	1,185,776
Income before income taxes	159,365	139,379	512,606	661,492
Income tax provision	57,311	54,012	193,001	250,793
Net income	$ 102,054	$ 85,367	$ 319,605	$ 410,699
Net income per common share
Basic	$ 0.28	$ 0.22	$ 0.87	$ 1.06
Diluted	$ 0.28	$ 0.22	$ 0.86	$ 1.05
Weighted average common shares outstanding
Basic	366,088	387,512	368,101	387,015
Diluted	369,142	390,909	371,316	390,854