CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 69,179	$ 50,148	$ 138,599	$ 90,694
Net change in foreign currency translation adjustment	1,199	83	740	(67)
Change in unrealized gains on investments, net of tax	27	323	42	1,475
Other comprehensive income	1,226	406	782	1,408
Comprehensive income	$ 70,405	$ 50,554	$ 139,381	$ 92,102