Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current deferred tax assets
Property and equipment	$ 233	$ 113
Other	869
Net operating loss carryforwards		13
Total current deferred tax assets	1,102	126
Valuation allowance on current deferred tax assets	(202)
Total current deferred tax assets, net of valuation allowance	900	126
Current deferred tax liabilities
Unrealized gain on derivatives	(1,311)	(2,998)
Other		(152)
Total current deferred tax liabilities	(1,311)	(3,150)
Net current deferred tax liability	(411)	(3,024)
Non-current deferred tax assets
Net operating loss carryforwards	44,654	24,034
Alternative minimum tax carryforwards	6,660	6,660
Total non-current deferred tax assets	51,314	30,694
Valuation allowance on non-current deferred tax assets	(10,058)
Total non-current deferred tax assets, net of valuation allowance	41,256	30,694
Non-current deferred tax liabilities
Property and equipment	(36,363)	(27,070)
Unrealized gain on derivatives	(262)	(324)
Other	(4,220)	(1,706)
Total non-current deferred tax liabilities	40,845	29,100
Net non-current deferred tax assets	$ 411	$ 1,594