CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 89,798	$ 69,191
Other comprehensive (loss) income, net of tax:
Change in unrealized investment gains and losses	12,121	50,827
Benefit plan adjustments	(153)	(308)
Foreign currency translation adjustment	31	(975)
Other comprehensive income, net of tax	11,999	49,544
Comprehensive income	$ 101,797	$ 118,735