Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 164,024	$ 187,032
Other comprehensive income (loss), net of tax:
Net changes in unrealized gains (losses) on available-for-sale investment securities	22,011	(18,812)
Foreign currency translation adjustments	3,180	6,798
Other comprehensive income (loss)	25,191	(12,014)
COMPREHENSIVE INCOME	$ 189,215	$ 175,018