Supplemental Information about Changes to Accumulated Other Comprehensive Income - Schedule of Reclassifications (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Unrealized investment (gains) losses on available for sale assets:
Realized (gains) losses	$ 27,788	$ 24,188	$ 65,676
Amortization of (discount) premium	(1,130,198)	(1,135,631)	(1,056,884)
Other operating expense	442,368	419,143	347,833
Total before tax	(1,435,975)	(1,326,637)	(1,194,266)
Tax	274,737	255,875	223,511
Total after-tax	(1,161,238)	(1,070,762)	(970,755)
Reclassification out of Accumulated Other Comprehensive Income
Unrealized investment (gains) losses on available for sale assets:
Total after-tax	11,825	3,348	63,080
Reclassification out of Accumulated Other Comprehensive Income | Unrealized investment (gains) losses on available for sale assets:
Unrealized investment (gains) losses on available for sale assets:
Realized (gains) losses	23,348	14,843	84,416
Amortization of (discount) premium	(8,634)	(11,079)	(4,178)
Total before tax	14,714	3,764	80,238
Tax	(3,090)	(790)	(16,850)
Total after-tax	11,624	2,974	63,388
Reclassification out of Accumulated Other Comprehensive Income | Pension adjustments:
Unrealized investment (gains) losses on available for sale assets:
Total before tax	253	474	(390)
Tax	(52)	(100)	82
Total after-tax	201	374	(308)
Reclassification out of Accumulated Other Comprehensive Income | Amortization of prior service cost
Unrealized investment (gains) losses on available for sale assets:
Other operating expense	1,168	1,071	1,075
Reclassification out of Accumulated Other Comprehensive Income | Amortization of actuarial (gain) loss
Unrealized investment (gains) losses on available for sale assets:
Other operating expense	$ (915)	$ (597)	$ (1,465)