CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 130,811	$ 176,934	$ 294,663	$ 496,653
Other comprehensive (loss) income, net of tax:
Change in unrealized investment gains and losses	33,712	31,372	104,308	183,197
Benefit plan adjustments	(11,347)	1,600	(9,239)	4,799
Other comprehensive (loss) income, net of tax	22,365	32,972	95,069	187,996
Comprehensive income	$ 153,176	$ 209,906	$ 389,732	$ 684,649