Derivative Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments
Total asset derivatives	$ 1,874	$ 1,120
Derivatives designated as hedging instruments under ASC 815
Derivative Instruments
Total asset derivatives	1,146	687
Derivatives designated as hedging instruments under ASC 815 | Foreign exchange contracts | Other current assets
Derivative Instruments
Total asset derivatives	850	545
Derivatives designated as hedging instruments under ASC 815 | Foreign exchange contracts | Other assets
Derivative Instruments
Total asset derivatives	94	142
Derivatives designated as hedging instruments under ASC 815 | Natural gas contracts | Other current assets
Derivative Instruments
Total asset derivatives	189
Derivatives designated as hedging instruments under ASC 815 | Natural gas contracts | Other assets
Derivative Instruments
Total asset derivatives	13
Derivatives not designated as hedging instruments under ASC 815 | Foreign exchange contracts | Other current assets
Derivative Instruments
Total asset derivatives	$ 728	$ 433