Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 113,981	$ 139,838
Other comprehensive gain, net of tax:
Foreign currency translation adjustments	3,397	3,377
Unrealized gain (loss) on investments:
Unrealized gains (losses) during the period, net of income taxes of $(240) and $424	797	(1,357)
Less: reclassification adjustment for losses (gains) realized in net income, net of income taxes of $(24) and $(15)	86	(273)
Unrealized gain (loss) on investments:	883	(1,630)
Total other comprehensive gain, net of tax	4,280	1,747
Comprehensive income	$ 118,261	$ 141,585

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

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