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	$ 103,284	$ 98,748	$ 210,800	$ 198,775
Other comprehensive income (loss), net of tax:
Net change in unrealized gains (losses) on available-for-sale investment securities	4,984	(8,125)	17,900	1,193
Foreign currency translation adjustments	(4,638)	0	(4,671)	0
Other comprehensive income (loss)	346	(8,125)	13,229	1,193
COMPREHENSIVE INCOME	$ 103,630	$ 90,623	$ 224,029	$ 199,968