Postretirement Benefits - Benefit Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Projected benefit obligation:
Projected benefit obligation, beginning of year	$ 1,272,654	$ 1,246,159
Service cost for benefits earned	50,242	53,041	$ 43,492
Interest cost on benefit obligation	39,764	36,824	37,578
Plan amendments	1,620	4,059
Actuarial gain	(448,330)	(38,400)
Benefits paid	(32,136)	(29,029)
Projected benefit obligation, end of year	883,814	1,272,654	$ 1,246,159
Accumulated benefit obligation, end of year	762,180	$ 1,037,820
Projected benefit obligations decrease	$ 388,800
Discount rate used to measure future benefit obligations (as a percent)	5.67%	3.16%