Accumulated Other Comprehensive Income Roll Forward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	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	$ (2,500)		$ 0
Unrealized gain on available-for-sale investments, net of tax (benefit)	(2,500)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(2,500)	$ 0
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	(22,780)		$ (29,090)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	6,310
Foreign currency translation adjustment	6,310	3,582
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(29,090)
Other Comprehensive Income Loss Arising During Period Total Net of Tax	3,810
Other comprehensive income, net of tax	3,810	$ 3,582
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	$ (25,280)