Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 58,069	$ 52,672
Other comprehensive income (loss), net of tax:
Unrealized gains on securities	25,451	31,827
Foreign currency translation adjustment	3,434	12,104
Pension benefit adjustment	3,533	3,596
Total other comprehensive income (loss), net of tax	32,418	47,527
Comprehensive income	90,487	100,199
Less: Comprehensive (loss) income attributable to noncontrolling interests	(206)	217
Comprehensive income attributable to the Company	$ 90,693	$ 99,982