Fair Value Measurements and Derivative Instruments (Derivative Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Total net derivative liability	$ (1,602)	$ (1,651)
Total derivative assets
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,386	1,358
Total derivative liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	(2,988)	(3,009)
Derivatives designated as hedging instruments | Foreign exchange contracts | Other current assets and prepayments
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	762	546
Derivatives designated as hedging instruments | Foreign exchange contracts | Accounts payable and accrued liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0	(526)
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other current assets and prepayments
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	624	812
Derivatives not designated as hedging instruments | Foreign exchange contracts | Accounts payable and accrued liabilities
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ (2,988)	$ (2,483)