Retirement Plans and Other Postretirement Benefits - Changes Benefit Obligations and Funded Status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Benefits
Change in Benefit Obligation
Benefit obligation at the beginning of the period	$ 2,809,529	$ 3,716,824
Service cost	39,461	55,473	$ 61,236
Interest cost	153,561	107,492	98,566
Benefit payments	(210,737)	(212,565)
Actuarial (gain) loss	116,249	(857,695)
Benefit obligation at the end of the period	2,908,063	2,809,529	3,716,824
Change in Plan Assets
Balance at the beginning of the period	2,829,485	3,812,041
Actual return/(loss) on plan assets	199,098	(787,874)
Benefit payments	(193,034)	(194,682)
Balance at the end of the period	2,835,549	2,829,485	3,812,041
Funded/(Underfunded) Status at the end of the period	(72,514)	19,956
Other Benefits
Change in Benefit Obligation
Benefit obligation at the beginning of the period	409,461	591,841
Service cost	8,567	16,470	17,796
Interest cost	22,509	17,491	16,513
Benefit payments	(30,784)	(30,913)
Actuarial (gain) loss	20,681	(185,428)
Benefit obligation at the end of the period	430,434	409,461	591,841
Change in Plan Assets
Balance at the beginning of the period	652,287	872,435
Actual return/(loss) on plan assets	67,317	(193,807)
Benefit payments	(23,110)	(26,341)
Balance at the end of the period	696,494	652,287	$ 872,435
Funded/(Underfunded) Status at the end of the period	$ 266,060	$ 242,826