CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 14,047	$ 167,778	$ 163,852	$ 319,719
Other comprehensive (loss) income, net of tax:
Change in unrealized investment gains and losses	143,181	70,754	70,596	151,825
Benefit plan adjustments	1,007	1,549	2,108	3,199
Other comprehensive (loss) income, net of tax	144,188	72,303	72,704	155,024
Comprehensive income	$ 158,235	$ 240,081	$ 236,556	$ 474,743