Derivative Instruments (Details 3) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Derivative Instruments
Total liability derivatives	$ 530	$ 646
Derivatives designated as hedging instruments under ASC 815
Derivative Instruments
Total liability derivatives	497	612
Derivatives designated as hedging instruments under ASC 815 | Foreign exchange contracts | Accounts payable and accrued liabilities
Derivative Instruments
Total liability derivatives	366	191
Derivatives designated as hedging instruments under ASC 815 | Foreign exchange contracts | Accrued pension and other liabilities
Derivative Instruments
Total liability derivatives	62	61
Derivatives designated as hedging instruments under ASC 815 | Natural gas forward contracts | Accounts payable and accrued liabilities
Derivative Instruments
Total liability derivatives	69	360
Derivatives not designated as hedging instruments under ASC 815 | Foreign exchange contracts | Accounts payable and accrued liabilities
Derivative Instruments
Total liability derivatives	$ 33	$ 34