Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 101,066	$ 126,540	$ 210,308	$ 240,521
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	940	(2,877)	(12,136)	520
Unrealized gain on investments:
Unrealized gains during the period, net of income taxes of $(33), $(230), $(372) and $(470)	113	765	1,244	1,562
Reclassification adjustment for losses realized in net income, net of income taxes of $(35), $(26), $(63) and $(50)	116	92	217	178
Unrealized gain on investments	229	857	1,461	1,740
Net current-period other comprehensive loss	1,169	(2,020)	(10,675)	2,260
Comprehensive income	$ 102,235	$ 124,520	$ 199,633	$ 242,781