CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 122,695	$ 85,071	$ (3,465)
Other comprehensive loss, net of tax
Foreign currency translation adjustment	3,901	(5,032)	(1,466)
Net decrease in unrealized loss on investments	118	395	256
Reclassification adjustment for realized gains on investments included in net income	0	(808)	0
Total other comprehensive income (loss)	4,019	(5,445)	(1,210)
Total comprehensive income (loss)	$ 126,714	$ 79,626	$ (4,675)