Condensed Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 43,996	$ 298
Restricted short-term investments	65	65
Accounts receivable	123,385	115,952
Deferred income taxes	18,973	13,779
Derivative instruments	283	6,117
Assets held for sale	0	14,622
Prepaid expenses and other	19,487	16,801
Total current assets	206,189	167,634
Oil and natural gas properties (successful efforts basis), buildings and equipment, net	2,650,904	2,531,393
Derivative instruments	276	7,027
Other assets	36,831	28,898
TOTAL ASSETS	2,894,200	2,734,952
Current liabilities:
Accounts payable	129,300	126,489
Revenue and royalties payable	25,412	49,253
Accrued liabilities	52,758	35,066
Derivative instruments	44,740	20,365
Total current liabilities	252,210	231,173
Long-term liabilities:
Deferred income taxes	207,992	185,450
Senior secured revolving credit facility	0	531,500
8.25% Senior subordinated notes due 2016	200,000	200,000
10.25% Senior notes due 2014, net of unamortized discount of $5,966 and $6,564, respectively	349,290	348,692
6.75% Senior notes due 2020	300,000	300,000
6.375% Senior notes due 2022	600,000	0
Asset retirement obligation	69,064	64,019
Derivative instruments	19,338	15,505
Other long-term liabilities	17,769	17,884
Total long-term liabilities	1,763,453	1,663,050
Shareholders' equity:
Preferred stock, $0.01 par value, 2,000,000 shares authorized; no shares outstanding	0	0
Capital in excess of par value	357,179	350,158
Accumulated other comprehensive loss	(4,250)	(5,517)
Retained earnings	525,066	495,549
Total shareholders' equity	878,537	840,729
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	2,894,200	2,734,952
Class A
Capital stock, $0.01 par value:
Common Stock	524	521
Class B
Capital stock, $0.01 par value:
Common Stock	$ 18	$ 18