Summary of Significant Accounting Policies - Inventories (Details 6) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Finished Goods	$ 24,732	$ 20,649
Work in Process	11,251	9,942
Raw Material, Fuel and Supplies	46,715	42,090
Total Inventories	$ 82,698	$ 72,681