Derivative instruments and hedging activities - Summary Of Notional Amounts Of Derivative Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Total forward contracts notional amount	$ 343,933	$ 318,974
Chinese yuan
Derivative [Line Items]
Total forward contracts notional amount	50,753	39,197
Euro
Derivative [Line Items]
Total forward contracts notional amount	188,001	177,406
Japanese yen
Derivative [Line Items]
Total forward contracts notional amount	20,145	22,857
Hungarian forint
Derivative [Line Items]
Total forward contracts notional amount	36,067	41,296
British pound
Derivative [Line Items]
Total forward contracts notional amount	8,498	9,931
Malaysian ringgit
Derivative [Line Items]
Total forward contracts notional amount	24,616	28,287
Korean won
Derivative [Line Items]
Total forward contracts notional amount	$ 15,853	$ 0