Derivatives - Amount of Gain (Loss) Recognized in OCI and Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain/(Loss) Recognized in OCI	$ 667	$ (144)	$ 3,541	$ 166
Derivatives designated as cash flow hedges | Interest rate swap
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain/(Loss) Recognized in OCI	664	1	3,532	(611)
Derivatives designated as cash flow hedges | Interest rate swap | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain/(Loss) Reclassified from AOCI	428	96	998	(8)
Derivatives designated as cash flow hedges | Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain/(Loss) Recognized in OCI		100		841
Derivatives designated as cash flow hedges | Foreign currency forward contracts | Revenue
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain/(Loss) Recognized in OCI	543		1,112
Amount of Gain/(Loss) Reclassified from AOCI	86	(101)	(299)	(141)
Derivatives designated as cash flow hedges | Foreign currency forward contracts | Cost of sales
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain/(Loss) Reclassified from AOCI	$ 26	$ 250	$ 404	$ 213