Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 171,416	$ 171,302	$ 485,820	$ 530,683
Other comprehensive income (loss), net of tax:
Net changes in unrealized gains (losses) on available-for-sale investment securities	11,863	(13,608)	62,901	(41,261)
Foreign currency translation adjustments	(2,858)	(4,761)	(5,694)	(4,785)
Other comprehensive income (loss)	9,005	(18,369)	57,207	(46,046)
COMPREHENSIVE INCOME	$ 180,421	$ 152,933	$ 543,027	$ 484,637