Income Taxes (Details 2) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Amount computed using the statutory rate	$ (102,257)	$ 9,887	$ 5,041
State & local taxes	(6,477)	904	317
Percentage depletion carryforward	(404)	(1,564)	(1,323)
Non-deductible stock option expense	90	213	115
Share-based compensation	1,317	90	780
Other	113	(643)	1,132
Change in valuation allowance	110,244	(11,828)	(5,742)
Income tax expense (benefit)	$ 2,626	$ (2,941)	$ 320