Derivative Instruments (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivative Instruments
Total liability derivatives	$ 190	$ 646
Derivatives designated as hedging instruments under ASC 815
Derivative Instruments
Total liability derivatives	150	612
Derivatives designated as hedging instruments under ASC 815 | Foreign exchange contracts | Accounts payable and accrued liabilities
Derivative Instruments
Total liability derivatives	58	191
Derivatives designated as hedging instruments under ASC 815 | Foreign exchange contracts | Accrued pension and other liabilities
Derivative Instruments
Total liability derivatives	9	61
Derivatives designated as hedging instruments under ASC 815 | Natural gas contracts | Accounts payable and accrued liabilities
Derivative Instruments
Total liability derivatives	83	360
Derivatives not designated as hedging instruments under ASC 815 | Foreign exchange contracts | Accounts payable and accrued liabilities
Derivative Instruments
Total liability derivatives	$ 40	$ 34