Derivative Instruments (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments
Total liability derivatives	$ 423	$ 646
Derivatives designated as hedging instruments under ASC 815
Derivative Instruments
Total liability derivatives	418	612
Derivatives designated as hedging instruments under ASC 815 | Foreign exchange contracts | Accounts payable and accrued liabilities
Derivative Instruments
Total liability derivatives	391	191
Derivatives designated as hedging instruments under ASC 815 | Foreign exchange contracts | Accrued pension and other liabilities
Derivative Instruments
Total liability derivatives	27	61
Derivatives designated as hedging instruments under ASC 815 | Natural gas forward contracts | Accounts payable and accrued liabilities
Derivative Instruments
Total liability derivatives		360
Derivatives not designated as hedging instruments under ASC 815 | Foreign exchange contracts | Accounts payable and accrued liabilities
Derivative Instruments
Total liability derivatives	$ 5	$ 34