Postretirement Benefits - Reconciliation of Benefit Obligation and Plan Assets, Pension Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Changes in PBO:
PBO at beginning of year	$ 627,560
Service cost	24,898	$ 21,568	$ 34,624
Interest cost	33,123	31,367	24,445
PBO at end of year	635,056	627,560
Pension Plan
Changes in PBO:
PBO at beginning of year	627,560	562,567
Service cost	24,898	21,568
Interest cost	33,123	31,367
Plan amendments	1,212	0
Actuarial loss (gain)	(22,964)	40,569
Benefits paid	(28,773)	(28,511)
PBO at end of year	635,056	627,560	562,567
Changes in plan assets:
Fair value at beginning of year	570,767	499,775
Return on assets	48,084	75,062
Contributions	24,767	24,441
Benefits paid	(28,773)	(28,511)
Fair value at end of year	614,845	570,767	$ 499,775
Funded status at year end	$ (20,211)	$ (56,793)