Condensed Consolidated Balance Sheets (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Current assets
Cash	$ 6,602	$ 54,937
Accounts receivable - net of allowance for doubtful accounts	61,270	63,380
Derivative assets at fair value	101,006	89,205
Other current assets	48,786	30,650
Total current assets	217,664	238,172
Investments in equity affiliates	21,725	83,341
Property, plant and equipment
Oil and gas properties, full cost method (including unevaluated costs of $460,158 and $304,269, respectively)	3,068,952	2,834,645
Other property and equipment	307,853	233,200
Property, plant and equipment - net	3,376,805	3,067,845
Assets of midstream operations held for sale		27,178
Derivative assets at fair value	106,844	57,557
Other assets	40,436	38,241
Total assets	3,763,474	3,512,334
LIABILITIES AND EQUITY
Current portion of long-term debt	149,331	143,478
Accounts payable	113,248	167,857
Accrued liabilities	123,937	122,904
Derivative liabilities at fair value	1,677
Current deferred tax liability	27,445	28,861
Total current liabilities	415,638	463,100
Long-term debt	1,930,529	1,746,716
Liabilities of midstream operations held for sale		1,431
Asset retirement obligations	58,223	56,235
Other liabilities	28,461	28,461
Deferred income taxes	212,829	156,983
Commitments and contingencies (Note 8)
Stockholders' equity
Preferred stock, par value $0.01, 10,000,000 shares authorized, none outstanding
Common stock, $0.01 par value, 400,000,000 shares authorized, and 176,894,542 and 175,524,816 shares issued, respectively	1,769	1,755
Paid in capital in excess of par value	731,063	714,869
Treasury stock of 5,376,615 and 5,050,450 shares, respectively	(46,328)	(41,487)
Accumulated other comprehensive income	110,691	130,187
Retained earnings	320,599	254,084
Total stockholders' equity	1,117,794	1,059,408
Total liabilities and equity	$ 3,763,474	$ 3,512,334