Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 703,701	$ 505,624	$ 431,677
Other comprehensive (loss) income, net of tax:
Net changes in unrealized losses on available-for-sale investment securities	(8,652)	(2,126)	(22,628)
Foreign currency translation adjustments	(5,732)	12,753	(10,577)
Other comprehensive (loss) income	(14,384)	10,627	(33,205)
COMPREHENSIVE INCOME	$ 689,317	$ 516,251	$ 398,472