CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets
Cash and cash equivalents	$ 14,422	$ 17,650
Accounts receivable, net of allowance for doubtful accounts	64,378	62,978
Derivative assets	5,900	11,292
Other current assets	3,961	4,595
Total current assets	88,661	96,515
Property and equipment, net (successful efforts method)	1,760,240	1,723,359
Derivative assets	3,608	5,181
Other assets	17,292	17,934
Total assets	1,869,801	1,842,989
Current liabilities
Accounts payable and accrued liabilities	121,967	111,655
Derivative liabilities	4,539	0
Deferred income taxes	573	370
Total current liabilities	127,079	112,025
Other liabilities	28,518	28,901
Derivative liabilities	1,235	1,421
Deferred income taxes	202,196	210,767
Long-term debt	633,080	594,759
Commitments and contingencies (Note 10)
Shareholders’ equity:
Preferred stock of $100 par value – 100,000 shares authorized; 11,500 shares issued as of March 31, 2013 and December 31, 2012 with a redemption value of $10,000 per share	1,150	1,150
Common stock of $0.01 par value – 128,000,000 shares authorized; 55,222,907 and 55,117,346 shares issued as of March 31, 2013 and December 31, 2012, respectively	365	364
Paid-in capital	849,710	849,046
Retained earnings	27,682	45,790
Deferred compensation obligation	3,176	3,111
Accumulated other comprehensive loss	(963)	(982)
Treasury stock – 234,253 and 218,320 shares of common stock, at cost, as of March 31, 2013 and December 31, 2012, respectively	(3,427)	(3,363)
Total shareholders’ equity	877,693	895,116
Total liabilities and shareholders’ equity	$ 1,869,801	$ 1,842,989