Fair Value Measurements and Derivative Instruments (Derivative Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Total net derivative liabilities	$ (3,692)	$ (1,602)
Total derivative assets
Derivative [Line Items]
Total net derivative liabilities	838	1,386
Total derivative liabilities
Derivative [Line Items]
Total net derivative liabilities	(4,530)	(2,988)
Foreign exchange contracts | Derivatives designated as hedging instruments | Other current assets and prepayments
Derivative [Line Items]
Total net derivative liabilities	518	762
Foreign exchange contracts | Derivatives designated as hedging instruments | Accounts payable and accrued liabilities:
Derivative [Line Items]
Total net derivative liabilities	(415)	0
Foreign exchange contracts | Derivatives not designated as hedging instruments | Other current assets and prepayments
Derivative [Line Items]
Total net derivative liabilities	320	624
Foreign exchange contracts | Derivatives not designated as hedging instruments | Accounts payable and accrued liabilities:
Derivative [Line Items]
Total net derivative liabilities	$ (4,115)	$ (2,988)