Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 4,413	$ 23,153
Accrued production receivable	163,942	181,761
Trade and other receivables, net	98,857	156,955
Derivative assets	268,025	440,359
Deferred tax assets, net	8,060	0
Other current assets	15,085	10,452
Total current assets	558,382	812,680
Oil and natural gas properties (using full cost accounting)
Proved properties	9,994,968	9,782,337
Unevaluated properties	936,736	918,406
CO2 properties	1,172,262	1,162,538
Pipelines and plants	2,279,813	2,269,564
Other property and equipment	466,362	468,051
Less accumulated depletion, depreciation, amortization and impairment	(6,388,348)	(4,248,652)
Net property and equipment	8,461,793	10,352,244
Derivative assets	696	66,187
Goodwill	1,261,512	1,283,590
Other assets	212,920	213,101
Total assets	10,495,303	12,727,802
Current liabilities
Accounts payable and accrued liabilities	228,942	394,758
Oil and gas production payable	114,953	128,170
Derivative liabilities	641	0
Deferred tax liabilities	0	81,727
Current maturities of long-term debt	38,105	35,470
Total current liabilities	382,641	640,125
Long-term liabilities
Long-term debt, net of current portion	3,471,141	3,535,900
Asset retirement obligations	132,213	126,411
Deferred tax liabilities	2,084,208	2,694,842
Other liabilities	25,066	26,668
Total long-term liabilities	$ 5,712,628	$ 6,383,821
Commitments and contingencies (Note 7)
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; 414,023,232 and 411,779,911 shares issued, respectively	414	412
Paid-in capital in excess of par	3,225,728	3,230,418
Retained earnings	2,092,350	3,392,465
Accumulated other comprehensive loss	(174)	(209)
Treasury stock, at cost, 58,667,781 and 58,415,507 shares, respectively	(918,284)	(919,230)
Total stockholders' equity	4,400,034	5,703,856
Total liabilities and stockholders' equity	$ 10,495,303	$ 12,727,802