Condensed Consolidated Balance Sheets (Unaudited) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Current assets
Cash and cash equivalents	$ 28,113,000	$ 18,693,000
Accrued production receivable	259,028,000	294,689,000
Trade and other receivables, net	170,536,000	164,446,000
Short-term investments	0	86,682,000
Derivative assets	57,764,000	47,402,000
Deferred tax assets	12,152,000	50,156,000
Other current assets	18,167,000	22,045,000
Total current assets	545,760,000	684,113,000
Oil and natural gas properties (using full cost accounting)
Proved	8,001,913,000	7,026,579,000
Unevaluated	777,141,000	1,157,106,000
CO2 properties	649,596,000	596,003,000
Pipelines and plants	1,875,847,000	1,701,756,000
Other property and equipment	396,847,000	157,674,000
Less accumulated depletion, depreciation, amortization, and impairment	(2,947,035,000)	(2,627,493,000)
Net property and equipment	8,754,309,000	8,011,625,000
Derivative assets	36,672,000	29,000
Goodwill	1,363,547,000	1,236,318,000
Other assets	235,128,000	252,339,000
Total assets	10,935,416,000	10,184,424,000
Current liabilities
Accounts payable and accrued liabilities	459,416,000	429,336,000
Oil and gas production payable	187,205,000	197,092,000
Derivative liabilities	1,816,000	26,523,000
Current maturities of long-term debt	36,168,000	8,316,000
Total current liabilities	684,605,000	661,267,000
Long-term liabilities
Long-term debt, net of current portion	2,942,070,000	2,669,729,000
Asset retirement obligations	86,572,000	88,726,000
Derivative liabilities	0	18,872,000
Deferred taxes	2,047,967,000	1,918,576,000
Other liabilities	21,005,000	20,756,000
Total long-term liabilities	5,097,614,000	4,716,659,000
Commitments and contingencies (Note 6)
Stockholders' equity
Preferred stock, $.001 par value, 25,000,000 shares authorized, none issued and outstanding	0	0
Common stock, $.001 par value, 600,000,000 shares authorized; 405,005,251 and 402,946,070 shares issued, respectively	405,000	403,000
Paid-in capital in excess of par	3,113,042,000	3,090,374,000
Retained earnings	2,234,807,000	1,909,475,000
Accumulated other comprehensive loss	(383,000)	(418,000)
Treasury stock, at cost, 13,961,181 and 13,965,673 shares, respectively	(194,674,000)	(193,336,000)
Total stockholders' equity	5,153,197,000	4,806,498,000
Total liabilities and stockholders' equity	$ 10,935,416,000	$ 10,184,424,000