Employee Benefit Plans and Other Postretirement Benefits - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension and SERPA Benefits
Defined Benefit Plan Disclosure
Service cost	$ 5,174	$ 19,052	$ 24,570
Interest cost	81,911	61,890	61,988
Expected return on plan assets	(146,076)	(125,904)	(131,494)
Prior service credit	751	(1,312)	(1,247)
Net loss	(722)	31,912	67,933
Curtailment (gain) loss	0	0	(10,562)
Settlement (gain) loss	(759)	(1,471)	722
Net periodic benefit cost	(59,721)	(15,833)	11,910
Postretirement Healthcare Benefits
Defined Benefit Plan Disclosure
Service cost	3,184	4,642	5,147
Interest cost	11,089	7,617	6,505
Expected return on plan assets	(17,124)	(15,237)	(13,978)
Prior service credit	(665)	(2,323)	(2,323)
Net loss	(4,388)	488	1,056
Curtailment (gain) loss	0	0	0
Settlement (gain) loss	0	(1,244)	0
Net periodic benefit cost	$ (7,904)	$ (6,057)	$ (3,593)