Fair Value Measurements and Derivative Instruments (Derivative Instruments) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Total net derivative asset (liabilities)	$ 485	$ 1,563
Total derivative assets
Derivative [Line Items]
Total net derivative asset (liabilities)	2,124	1,898
Total derivative liabilities
Derivative [Line Items]
Total net derivative asset (liabilities)	(1,639)	(335)
Foreign exchange contracts | Derivatives designated as hedging instruments | Other current assets and prepayments
Derivative [Line Items]
Total net derivative asset (liabilities)	103	57
Foreign exchange contracts | Derivatives designated as hedging instruments | Accounts payable and accrued liabilities
Derivative [Line Items]
Total net derivative asset (liabilities)	(69)	(144)
Foreign exchange contracts | Derivatives not designated as hedging instruments | Other current assets and prepayments
Derivative [Line Items]
Total net derivative asset (liabilities)	426	65
Foreign exchange contracts | Derivatives not designated as hedging instruments | Accounts payable and accrued liabilities
Derivative [Line Items]
Total net derivative asset (liabilities)	(1,570)	(191)
Interest rate swap | Derivatives designated as hedging instruments | Other current assets and prepayments
Derivative [Line Items]
Total net derivative asset (liabilities)	$ 1,595	$ 1,776