Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Assets
Cash and cash equivalents	$ 34,589	$ 55,111
Accounts receivable, net	64,788	62,780
Inventories	8,641	11,068
Prepaid expenses	3,265	2,429
Derivative instruments	12,840	1,429
Deferred income taxes	0	9,531
Total current assets	124,123	142,348
Property and equipment—at cost, net	65,711	66,014
Oil and natural gas properties, using the full cost method:
Proved	2,535,404	2,253,662
Unevaluated (excluded from the amortization base)	22,831	19,135
Accumulated depreciation, depletion, amortization and impairment	(1,135,567)	(1,003,261)
Total oil and natural gas properties	1,422,668	1,269,536
Derivative instruments	16,785	0
Deferred income taxes	7,526	20,617
Other assets	32,920	30,777
Total assets	1,669,733	1,529,292
Liabilities and stockholders' equity
Accounts payable and accrued liabilities	68,930	75,982
Accrued payroll and benefits payable	18,818	13,427
Accrued interest payable	30,882	23,695
Revenue distribution payable	20,800	17,223
Current maturities of long-term debt and capital leases	3,078	4,167
Derivative instruments	1,505	28,853
Deferred income taxes	23,704	0
Total current liabilities	167,717	163,347
Long-term debt and capital leases, less current maturities	1,031,495	957,920
Derivative instruments	127	2,482
Stock-based compensation	2,788	981
Asset retirement obligations	43,593	41,005
Commitments and contingencies (Note 14)
Stockholders' equity:
Preferred stock, 600,000 shares authorized, none issued and outstanding	0	0
Additional paid in capital	419,370	417,834
Accumulated deficit	(47,217)	(89,265)
Accumulated other comprehensive income, net of taxes	51,846	34,974
Total stockholders' equity	424,013	363,557
Total liabilities and stockholders' equity	1,669,733	1,529,292
Common Class A [Member]
Stockholders' equity:
Common stock	0	0
Common Class B [Member]
Stockholders' equity:
Common stock	4	4
Common Class C [Member]
Stockholders' equity:
Common stock	2	2
Common Class D [Member]
Stockholders' equity:
Common stock	3	3
Common Class E [Member]
Stockholders' equity:
Common stock	5	5
Common Class F [Member]
Stockholders' equity:
Common stock	0	0
Common Class G [Member]
Stockholders' equity:
Common stock	$ 0	$ 0