Retirement Plans and Other Postretirement Benefits - Schedule of Net Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Amortization of:
Portion of cost/(benefit) charged to expense	$ (12,877)	$ (10,474)	$ (24,445)	$ (20,339)
Pension Benefits
Retirement Plans and Other Benefits
Service cost — benefits earned during the period	11,190	9,573	21,821	19,730
Interest cost on benefit obligation	37,085	38,418	74,321	76,780
Expected return on plan assets	(47,342)	(45,908)	(94,325)	(91,469)
Amortization of:
Prior service credit	0	0	0	0
Net actuarial loss/(gain)	10,014	9,497	20,958	19,210
Net periodic cost/(benefit)	10,947	11,580	22,775	24,251
Portion of cost/(benefit) charged to expense	5,500	6,513	11,837	13,740
Other Benefits
Retirement Plans and Other Benefits
Service cost — benefits earned during the period	2,518	2,164	4,977	4,284
Interest cost on benefit obligation	5,472	5,582	11,085	11,255
Expected return on plan assets	(11,708)	(10,872)	(23,417)	(21,744)
Amortization of:
Prior service credit	(9,447)	(9,447)	(18,894)	(18,894)
Net actuarial loss/(gain)	(2,258)	(2,504)	(4,338)	(4,807)
Net periodic cost/(benefit)	(15,423)	(15,077)	(30,587)	(29,906)
Portion of cost/(benefit) charged to expense	$ (11,515)	$ (10,948)	$ (22,821)	$ (21,685)