Supplemental Information about Changes to Accumulated Other Comprehensive Income - Schedule of Reclassifications (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Unrealized investment (gains) losses on available for sale assets:
Realized (gains) losses	$ 24,188	$ 65,676	$ 76,548
Net investment income	(1,135,631)	(1,056,884)	(991,800)
Other operating expense	419,143	347,833	353,954
Total before tax	(1,326,637)	(1,194,266)	(1,102,111)
Tax	255,875	223,511	207,725
Total after-tax	(1,070,762)	(970,755)	(894,386)
Reclassification out of Accumulated Other Comprehensive Income
Unrealized investment (gains) losses on available for sale assets:
Total after-tax	3,348	63,080	36,443
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Available for Sale Assets
Unrealized investment (gains) losses on available for sale assets:
Realized (gains) losses	14,843	84,416	32,165
Net investment income	(11,079)	(4,178)	212
Total before tax	3,764	80,238	32,377
Tax	(790)	(16,850)	(6,799)
Total after-tax	2,974	63,388	25,578
Reclassification out of Accumulated Other Comprehensive Income | Pension adjustments:
Unrealized investment (gains) losses on available for sale assets:
Total before tax	474	(390)	13,754
Tax	(100)	82	(2,889)
Total after-tax	374	(308)	10,865
Reclassification out of Accumulated Other Comprehensive Income | Amortization of prior service cost
Unrealized investment (gains) losses on available for sale assets:
Other operating expense	1,071	1,075	1,077
Reclassification out of Accumulated Other Comprehensive Income | Amortization of actuarial (gain) loss
Unrealized investment (gains) losses on available for sale assets:
Other operating expense	$ (597)	$ (1,465)	$ 12,677