Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Assets
Cash and cash equivalents	$ 32,997	$ 34,589
Accounts receivable, net	79,450	64,788
Inventories	13,240	8,641
Prepaid expenses	2,051	3,265
Derivative instruments	35,310	12,840
Total current assets	163,048	124,123
Property and equipment—at cost, net	74,872	65,711
Oil and natural gas properties, using the full cost method:
Proved	2,777,469	2,535,404
Unevaluated (excluded from the amortization base)	134,388	22,831
Accumulated depreciation, depletion, amortization and impairment	(1,244,560)	(1,135,567)
Total oil and natural gas properties	1,667,297	1,422,668
Derivative instruments	7,208	16,785
Deferred income taxes	0	7,526
Other assets	35,522	32,920
Total assets	1,947,947	1,669,733
Liabilities and stockholders' equity
Accounts payable and accrued liabilities	120,342	68,930
Accrued payroll and benefits payable	18,898	18,818
Accrued interest payable	30,566	30,882
Revenue distribution payable	18,584	20,800
Current maturities of long-term debt and capital leases	4,027	3,078
Derivative instruments	536	1,505
Deferred income taxes	25,736	23,704
Total current liabilities	218,689	167,717
Long-term debt, less current maturities	1,226,392	1,031,495
Derivative instruments	1,263	127
Stock-based compensation	2,674	2,788
Asset retirement obligations, net of current portion	45,621	43,593
Deferred income taxes	1,264	0
Commitments and contingencies (Note 10)
Stockholders' equity:
Preferred stock, 600,000 shares authorized, none issued and outstanding	0	0
Additional paid in capital	423,162	419,370
Accumulated deficit	(1,918)	(47,217)
Accumulated other comprehensive income, net of taxes	30,786	51,846
Total stockholders' equity	452,044	424,013
Total liabilities and stockholders' equity	1,947,947	1,669,733
Common Class A
Stockholders' equity:
Common stock	0	0
Common Class B
Stockholders' equity:
Common stock	4	4
Common Class C
Stockholders' equity:
Common stock	2	2
Common Class D
Stockholders' equity:
Common stock	3	3
Common Class E
Stockholders' equity:
Common stock	5	5
Common Class F
Stockholders' equity:
Common stock	0	0
Common Class G
Stockholders' equity:
Common stock	$ 0	$ 0