Income Taxes (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current income tax provision (benefit)
State income tax	$ 0	$ 0	$ (46)
Federal alternative minimum tax	404	0	0
Net current income tax provision (benefit)	404	0	(46)
Deferred income tax provision (benefit)
Federal tax expense at statutory rate	19,177	(11,767)	(5,319)
Statutory depletion carryforward	0	0	231
State income tax	431	(819)	(435)
Nondeductible expense	0	(122)	48
Permanent differences	319	1,018	0
Federal alternative minimum tax	(404)	0	0
Change in federal valuation allowance	(8,885)	10,260	0
Change in state valuation allowance	(1,345)	0	0
Net deferred income tax provision (benefit)	9,293	(1,430)	(5,475)
Total income tax provision (benefit)	$ 9,697	$ (1,430)	$ (5,521)
Federal statutory rate	35.00%	34.00%	34.00%