Retirement Plans and Other Postretirement Benefits - Schedule of Net Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Amortization of:
Portion of cost/(benefit) charged to expense	$ (11,568)	$ (9,865)
Pension Benefits
Retirement Plans and Other Benefits
Service cost — benefits earned during the period	10,631	10,157
Interest cost on benefit obligation	37,236	38,362
Expected return on plan assets	(46,983)	(45,561)
Amortization of:
Prior service credit (a)	0	0
Net actuarial loss/(gain)	10,944	9,713
Net periodic cost/(benefit)	11,828	12,671
Portion of cost/(benefit) charged to expense	6,337	7,227
Other Benefits
Retirement Plans and Other Benefits
Service cost — benefits earned during the period	2,459	2,120
Interest cost on benefit obligation	5,613	5,673
Expected return on plan assets	(11,709)	(10,872)
Amortization of:
Prior service credit (a)	(9,447)	(9,447)
Net actuarial loss/(gain)	(2,080)	(2,303)
Net periodic cost/(benefit)	(15,164)	(14,829)
Portion of cost/(benefit) charged to expense	$ (11,306)	$ (10,737)