CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Current assets
Cash and cash equivalents	$ 11,532	$ 7,512
Accounts receivable, net of allowance for doubtful accounts	55,751	72,432
Derivative assets	26,763	18,987
Income taxes receivable	31,154	31,465
Other current assets	6,850	14,950
Total current assets	132,050	145,346
Property and equipment, net (successful efforts method)	1,811,553	1,777,575
Derivative assets	12,664	0
Other assets	20,805	20,132
Total assets	1,977,072	1,943,053
Current liabilities
Accounts payable and accrued liabilities	84,222	94,504
Derivative liabilities	617	3,549
Deferred income taxes	3,807	3,808
Current portion of long-term debt	4,837	4,746
Total current liabilities	93,483	106,607
Other liabilities	16,575	15,887
Derivative liabilities	1,651	6,850
Deferred income taxes	264,631	274,839
Long-term debt	774,144	692,561
Commitments and contingencies (Note 10)
Shareholders' equity:
Preferred stock of $100 par value - 100,000 shares authorized; none issued	0	0
Common stock of $0.01 par value - 128,000,000 shares authorized; shares issued of 45,877,121 and 45,714,191 as of June 30, 2012 and December 31, 2011, respectively	271	270
Paid-in capital	693,078	690,131
Retained earnings	134,529	157,242
Deferred compensation obligation	3,032	3,620
Accumulated other comprehensive loss	(1,038)	(1,084)
Treasury stock - 202,875 and 223,886 shares of common stock, at cost, as of June 30, 2012 and December 31, 2011, respectively	(3,284)	(3,870)
Total shareholders' equity	826,588	846,309
Total liabilities and shareholders' equity	$ 1,977,072	$ 1,943,053