CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 431,677	$ 384,677	$ 345,878
Other comprehensive (loss) income, net of tax:
Net change in unrealized (losses) gains on available-for-sale investment securities	(22,628)	(10,381)	34,696
Foreign currency translation adjustments	(10,577)	(8,797)	0
Other comprehensive (loss) income	(33,205)	(19,178)	34,696
COMPREHENSIVE INCOME	$ 398,472	$ 365,499	$ 380,574