Fair Value Measurements and Derivative Instruments (Derivative Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Total net derivative liabilities	$ (1,871)	$ (1,602)
Total derivative assets
Derivative [Line Items]
Total net derivative liabilities	2,834	1,386
Total derivative liabilities
Derivative [Line Items]
Total net derivative liabilities	(4,705)	(2,988)
Foreign exchange contracts | Derivatives designated as hedging instruments | Other current assets and prepayments
Derivative [Line Items]
Total net derivative liabilities	1,144	762
Foreign exchange contracts | Derivatives not designated as hedging instruments | Other current assets and prepayments
Derivative [Line Items]
Total net derivative liabilities	1,690	624
Foreign exchange contracts | Derivatives not designated as hedging instruments | Accounts payable and accrued liabilities:
Derivative [Line Items]
Total net derivative liabilities	$ (4,705)	$ (2,988)