Employee and Retiree Benefit Plans - Components of Net Periodic Benefit Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,706	$ 1,650	$ 3,412	$ 3,300
Interest cost	8,393	8,564	16,784	17,071
Expected return on plan assets	(8,359)	(8,254)	(16,716)	(16,448)
Estimated defined contribution provision	54	54	109	108
Amortization of prior service cost (credit)	579	155	1,158	310
Recognized actuarial loss (gain)	2,361	2,414	4,721	4,815
Total net periodic benefit expense	4,734	4,583	9,468	9,156
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	135	132	270	264
Interest cost	782	874	1,564	1,748
Expected return on plan assets	0	0	0	0
Estimated defined contribution provision	0	0	0	0
Amortization of prior service cost (credit)	(133)	(133)	(266)	(266)
Recognized actuarial loss (gain)	(812)	(767)	(1,624)	(1,548)
Total net periodic benefit expense	$ (28)	$ 106	$ (56)	$ 198