Hedging - Notional Amount (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative term	1 month
Designated as hedging instruments | Cash Flow Hedging | Foreign currency forward contracts
Derivative [Line Items]
Notional amount of foreign currency forward contract	$ 505,218	$ 365,212
Designated as hedging instruments | Cash Flow Hedging | Foreign currency forward contracts | Euro
Derivative [Line Items]
Notional amount of foreign currency forward contract	335,179	257,230
Designated as hedging instruments | Cash Flow Hedging | Foreign currency forward contracts | British pound sterling
Derivative [Line Items]
Notional amount of foreign currency forward contract	73,460	77,481
Designated as hedging instruments | Cash Flow Hedging | Foreign currency forward contracts | Australian dollar
Derivative [Line Items]
Notional amount of foreign currency forward contract	52,820	30,501
Designated as hedging instruments | Cash Flow Hedging | Foreign currency forward contracts | Canadian dollar
Derivative [Line Items]
Notional amount of foreign currency forward contract	$ 43,759	$ 0
Minimum | Cash Flow Hedging | Foreign currency forward contracts
Derivative [Line Items]
Derivative term	1 month
Maximum | Cash Flow Hedging | Foreign currency forward contracts
Derivative [Line Items]
Derivative term	18 months