CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 31,350	$ 35,600	$ 67,527	$ 68,044
Net change in cumulative translation adjustment	52	(4)	(209)	102
Change in unrealized gains (losses) on available-for-sale securities, net of tax	(133)	70	162	112
Other comprehensive income (loss)	(81)	66	(47)	214
Comprehensive income	$ 31,269	$ 35,666	$ 67,480	$ 68,258