Accumulated Other Comprehensive Income Roll Forward (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) Roll Forward [Line Items]
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	$ (1,577)		$ (1,577)		$ (2,500)	$ 0
Unrealized gain on available-for-sale investments, net of tax (benefit)	923		(1,577)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	923	$ 0	(1,577)	$ 0
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	(37,428)		(37,428)		$ (22,780)	$ (29,090)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(14,648)		(8,338)
Foreign currency translation adjustment	(14,648)	12,331	(8,338)	15,913
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(25,280)		(29,090)
Other Comprehensive Income Loss Arising During Period Total Net of Tax	(13,725)		(9,915)
Other comprehensive (loss) income, net of tax	(13,725)	$ 12,331	(9,915)	$ 15,913
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	$ (39,005)		$ (39,005)