CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 50,148	$ 31,350	$ 90,694	$ 67,527
Net change in cumulative translation adjustment	83	52	(67)	(209)
Change in unrealized gains (losses) on available-for-sale securities, net of tax	323	(133)	1,475	162
Other comprehensive income (loss)	406	(81)	1,408	(47)
Comprehensive income	$ 50,554	$ 31,269	$ 92,102	$ 67,480