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Derivative Instruments (Details 1) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Schedule of fair value of outstanding derivative instruments recorded as assets and liability    
Liability Derivatives, not designated or not qualifying as hedging instruments $ 2,192 $ 4,003
Energy contracts and options [Member] | Other current assets [Member]    
Schedule of fair value of outstanding derivative instruments recorded as assets and liability    
Asset Derivatives, not designated or not qualifying as hedging instruments 1,681 2,377
Energy contracts and options [Member] | Energy hedging contracts [Member]    
Schedule of fair value of outstanding derivative instruments recorded as assets and liability    
Liability Derivatives, not designated or not qualifying as hedging instruments $ 2,192 $ 4,003