Financial Instruments - Location and fair value of derivative instruments qualifying as cash flow hedges (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Derivative Instruments in Hedges, Assets, at Fair Value	$ 377	$ 389
Derivative Instruments in Hedges, Liabilities, at Fair Value	(5,770)	(3,653)
Other Current Assets [Member] | Foreign exchange contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	288	370
Other Current Assets [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	36	0
Other Assets [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	53	19
Accrued Liabilities [Member] | Foreign exchange contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Current	(906)	(1,999)
Accrued Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Current	(3,056)	(751)
Other Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	$ (1,808)	$ (903)