CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 149,805	$ 151,941
Other comprehensive (loss) income, net of tax:
Change in unrealized investment gains and losses	(72,585)	81,071
Benefit plan adjustments	1,101	1,650
Other comprehensive (loss) income, net of tax	(71,484)	82,721
Comprehensive income	$ 78,321	$ 234,662