Derivative Instruments Fair Value of Derivative Instruments on the Consolidated Balance Sheets (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Total derivatives	$ 417	$ 626
Total derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Total derivatives	409	667
Total derivatives designated as hedging instruments | Commodity contracts | Prepaid and other current assets
Derivatives, Fair Value [Line Items]
Total derivatives	409	667
Total derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Total derivatives	8	(41)
Total derivatives not designated as hedging instruments | Commodity contracts | Prepaid and other current assets
Derivatives, Fair Value [Line Items]
Total derivatives	139	97
Total derivatives not designated as hedging instruments | Interest rate swap agreements | Other liabilities
Derivatives, Fair Value [Line Items]
Total derivatives	$ (131)	$ (138)