Financial Instruments Measured at Fair Value - Fair Value Hierarchy (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	$ 854	$ 2,660
Available-for-sale securities	45,112	37,915
Interest rate swaps - asset	180	152
Foreign exchange contracts - asset	6,809	4,685
Foreign exchange contracts - liability	(6,733)	(3,444)
Contingent consideration	(3,100)	(4,027)
Total Fair Value Assets And Liabilities Measured On Recurring Basis	43,122	37,941
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	854	2,660
Available-for-sale securities	45,112	37,915
Interest rate swaps - asset	0	0
Foreign exchange contracts - asset	0	0
Foreign exchange contracts - liability	0	0
Contingent consideration	0	0
Total Fair Value Assets And Liabilities Measured On Recurring Basis	45,966	40,575
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	0	0
Available-for-sale securities	0	0
Interest rate swaps - asset	180	152
Foreign exchange contracts - asset	6,809	4,685
Foreign exchange contracts - liability	(6,733)	(3,444)
Contingent consideration	0	0
Total Fair Value Assets And Liabilities Measured On Recurring Basis	256	1,393
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	0	0
Available-for-sale securities	0	0
Interest rate swaps - asset	0	0
Foreign exchange contracts - asset	0	0
Foreign exchange contracts - liability	0	0
Contingent consideration	(3,100)	(4,027)
Total Fair Value Assets And Liabilities Measured On Recurring Basis	$ (3,100)	$ (4,027)