Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets
Cash	$ 23,055	$ 23,726
Accounts receivable, net
Oil and gas sales	52,766	29,684
Joint interest owners	23,280	21,876
Other	818	4,590
Other current assets	1,687	1,088
Commodity derivative assets	14,681	17,648
Total current assets	116,287	98,612
Oil and gas properties, net, at cost under the successful efforts method	1,080,054	1,007,344
Other property, plant and equipment, net	2,479	3,398
Commodity derivative assets	26,591	25,199
Other assets	15,345	16,133
Deferred tax assets	359
Total assets	1,241,115	1,150,686
Current liabilities
Trade accounts payable	58,516	38,036
Oil and gas sales payable	63,858	45,860
Accrued liabilities	7,796	3,873
Deferred tax liabilities	17	61
Asset retirement obligations	174	174
Commodity derivative liabilities	10,424	4,035
Total current liabilities	140,785	92,039
Long-term debt	438,000	610,000
Deferred revenue	14,886
Commodity derivative liabilities	511	7,657
Asset retirement obligations	10,025	9,332
Deferred tax liabilities	2,138	1,876
Total liabilities	606,345	720,904
Commitments and contingencies (Note 10)
Stockholders' / members' equity
Members' equity		429,782
Additional paid-in-capital	172,652
Retained earnings	(821)
Stockholders' / members' equity	171,881	429,782
Non-controlling interest	462,889
Total stockholders' / members' equity	634,770	429,782
Total liabilities and stockholders' / members' equity	1,241,115	1,150,686
Class A common stock
Stockholders' / members' equity
Common stock	13
Class B common stock
Stockholders' / members' equity
Common stock	$ 37