CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 69,420	$ 40,546
Net change in foreign currency translation adjustment	(459)	(150)
Change in unrealized gains on investments, net of tax	15	1,152
Other comprehensive income (loss)	(444)	1,002
Comprehensive income	$ 68,976	$ 41,548