Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 171,302	$ 132,660	$ 530,683	$ 420,726
Other comprehensive (loss) income, net of tax:
Net changes in unrealized (losses) gains on available-for-sale investment securities	(13,608)	(1,906)	(41,261)	7,916
Foreign currency translation adjustments	(4,761)	3,870	(4,785)	8,013
Other comprehensive (loss) income	(18,369)	1,964	(46,046)	15,929
COMPREHENSIVE INCOME	$ 152,933	$ 134,624	$ 484,637	$ 436,655