Hedging - Cash Flow Hedging Instruments (Details) - Unrealized Holding Gains (Losses), Net of Tax, On Foreign Currency Forward Contracts - Reclassification out of Accumulated Other Comprehensive Income - Foreign currency forward contracts - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Revenues	$ 8,238	$ (2,675)	$ 15,077	$ (9,159)
Not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Other Income	$ (1,089)	$ (4,152)	$ 2,062	$ (2,614)