Other Comprehensive Income (Loss) - Pretax Components of Other Comprehensive Income (Loss) and Related Income Tax Benefit (Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Components of Other Comprehensive Income (Loss) [Abstract]
Net unrealized investment (losses) gains arising during the period	$ (707,005)	$ (154,555)	$ 169,135
Income tax benefit (expense)	148,471	32,456	(35,519)
Net of taxes	(558,534)	(122,099)	133,616
Net changes in benefit plan assets and obligations	(54,017)	31,613	13,288
Income tax benefit (expense)	11,343	(6,638)	(2,791)
Net of taxes	(42,674)	24,975	10,497
Total other comprehensive income (loss)	(761,022)	(122,942)	182,423
Total income tax benefit (expense)	159,814	25,818	(38,310)
Other comprehensive income (loss), net of tax	$ (601,208)	$ (97,124)	$ 144,113