Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current deferred tax assets
Property and equipment	$ 62	$ 233
Unrealized loss on derivatives	965	0
Other	609	869
Total current deferred tax assets	1,636	1,102
Valuation allowance on current deferred tax assets	0	(202)
Total current deferred tax assets, net of valuation allowance	1,636	900
Current deferred tax liabilities
Unrealized gain on derivatives	0	(1,311)
Net current deferred tax assets (liabilities)	1,636	(411)
Non-current deferred tax assets
Unrealized loss on derivatives	28	0
Net operating loss carryforwards	63,007	44,654
Alternative minimum tax carryforwards	7,064	6,660
Total non-current deferred tax assets	70,099	51,314
Valuation allowance on non-current deferred tax assets	(30)	(10,058)
Total non-current deferred tax assets, net of valuation allowance	70,069	41,256
Non-current deferred tax liabilities
Unrealized gain on derivatives	0	(262)
Property and equipment	(76,719)	(36,363)
Other	(4,279)	(4,220)
Total non-current deferred tax liabilities	(80,998)	(40,845)
Net non-current deferred tax (liabilities) assets	$ (10,929)	$ 411