Financial Instruments and Concentrations of Risk (Details 3) - Not Designated as Hedging Instrument [Member] - Commodity Contract [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	$ 0	$ 1,674
Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	$ 339	$ 0