Derivative Instruments Fair Value of Derivative Instruments on the Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Total derivatives	$ 743	$ 626
Total derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Total derivatives	603	667
Total derivatives designated as hedging instruments | Commodity contracts | Prepaid and other current assets
Derivatives, Fair Value [Line Items]
Total derivatives	603	667
Total derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Total derivatives	140	(41)
Total derivatives not designated as hedging instruments | Commodity contracts | Prepaid and other current assets
Derivatives, Fair Value [Line Items]
Total derivatives	243	97
Total derivatives not designated as hedging instruments | Interest rate swap agreements | Other liabilities
Derivatives, Fair Value [Line Items]
Total derivatives	$ (103)	$ (138)