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Derivative Instruments (Details 1) - USD ($) $ in Thousands | Dec. 31, 2015 | Dec. 31, 2014
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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

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