CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 238,334	$ 122,695	$ 85,071
Other comprehensive (loss) income, net of tax
Foreign currency translation adjustment	(2,668)	3,901	(5,032)
Net decrease in unrealized loss on investments	0	118	395
Reclassification adjustment for realized gains on investments included in net income	0	0	(808)
Total other comprehensive (loss) income	(2,668)	4,019	(5,445)
Total comprehensive income	$ 235,666	$ 126,714	$ 79,626