Summary of Significant Accounting Policies - Inventories (Details 1) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Finished Goods	$ 21,888	$ 25,971
Work in Process	13,774	12,821
Raw Material, Fuel and Supplies	45,186	46,624
Total Inventories	$ 80,848	$ 85,416