Derivative Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivative Instruments
Total asset derivatives	$ 1,606	$ 1,120
Derivatives designated as hedging instruments under ASC 815
Derivative Instruments
Total asset derivatives	1,182	687
Derivatives designated as hedging instruments under ASC 815 | Foreign exchange contracts | Other current assets
Derivative Instruments
Total asset derivatives	1,045	545
Derivatives designated as hedging instruments under ASC 815 | Foreign exchange contracts | Other assets
Derivative Instruments
Total asset derivatives	132	142
Derivatives designated as hedging instruments under ASC 815 | Natural gas contracts | Other current assets
Derivative Instruments
Total asset derivatives	5
Derivatives not designated as hedging instruments under ASC 815 | Foreign exchange contracts | Other current assets
Derivative Instruments
Total asset derivatives	$ 424	$ 433