Retirement Plans and Other Postretirement Benefits - Schedule of Net Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Amortization of:
Portion of cost/(benefit) charged to expense	$ (10,174)	$ (24,673)	$ (30,513)	$ (73,739)
Pension Benefits
Retirement Plans and Other Benefits
Service cost — benefits earned during the period	9,865	13,868	29,595	41,605
Interest cost on benefit obligation	38,390	26,873	115,170	80,619
Expected return on plan assets	(45,735)	(46,443)	(137,204)	(139,331)
Amortization of:
Prior service credit	0	0	0	0
Net actuarial loss/(gain)	9,605	4,379	28,815	13,136
Net periodic cost/(benefit)	12,125	(1,323)	36,376	(3,971)
Portion of cost/(benefit) charged to expense	6,828	(4,246)	20,568	(12,258)
Other Benefits
Retirement Plans and Other Benefits
Service cost — benefits earned during the period	2,142	4,117	6,426	12,352
Interest cost on benefit obligation	5,627	4,372	16,882	13,118
Expected return on plan assets	(10,872)	(11,510)	(32,616)	(34,531)
Amortization of:
Prior service credit	(9,447)	(9,447)	(28,341)	(28,341)
Net actuarial loss/(gain)	(2,404)	(3,209)	(7,211)	(9,627)
Net periodic cost/(benefit)	(14,954)	(15,677)	(44,860)	(47,029)
Portion of cost/(benefit) charged to expense	$ (10,851)	$ (11,318)	$ (32,536)	$ (33,736)