Retirement Plans and Other Postretirement Benefits - Net Periodic Benefit Costs and Portion including Portion Charged to Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net periodic benefit costs and the portion of these costs charged to expense
Portion of cost/(benefit) charged to expense	$ (40,648)	$ (98,487)	$ (112,541)
Pension Benefits
Net periodic benefit costs and the portion of these costs charged to expense
Service cost-benefits earned during the period	39,461	55,473	61,236
Interest cost on benefit obligation	153,561	107,492	98,566
Expected return on plan assets	(182,938)	(185,775)	(202,628)
Prior service credit (a)	0	0	0
Net actuarial (gain)/loss	38,420	17,515	15,948
Net periodic benefit cost/(benefit)	48,504	(5,295)	(26,878)
Portion of cost/(benefit) charged to expense	27,029	(16,431)	(32,743)
Other Benefits
Net periodic benefit costs and the portion of these costs charged to expense
Service cost-benefits earned during the period	8,567	16,470	17,796
Interest cost on benefit obligation	22,509	17,491	16,513
Expected return on plan assets	(43,486)	(46,042)	(41,444)
Prior service credit (a)	(37,789)	(37,789)	(37,705)
Net actuarial (gain)/loss	(9,614)	(12,835)	(10,093)
Net periodic benefit cost/(benefit)	(59,813)	(62,705)	(54,933)
Portion of cost/(benefit) charged to expense	$ (43,408)	$ (45,042)	$ (38,657)