Benefit Plans - Reconciliation of Funded Status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Change in plan assets
Fair value of assets at beginning of year	$ 269,912
Fair value of plan assets at end of year	306,711	$ 269,912
Pension Benefits
Change in benefit obligation
Benefit obligation at beginning of year	289,123	383,838
Service cost	7,569	9,359	$ 9,730
Interest cost	14,234	10,708	9,415
Actuarial loss/(gain)	5,794	(94,793)
Implicit rate subsidy	0	0
Plan participants contributions	0	0
Administrative expenses paid	(137)	(136)
Benefits paid and settlements	(18,749)	(19,853)
Benefit obligation at end of year	297,834	289,123	383,838
Change in plan assets
Fair value of assets at beginning of year	251,960	310,176
Actual return on plan assets	41,285	(49,939)
Employer contributions	11,145	11,712
Plan participants contributions	0	0
Administrative expenses paid	(137)	(136)
Benefits paid and settlements	(18,749)	(19,853)
Fair value of plan assets at end of year	285,504	251,960	310,176
Funded status at end of year	(12,330)	(37,163)
Other Postretirement Benefits
Change in benefit obligation
Benefit obligation at beginning of year	25,830	34,412
Service cost	638	1,032	1,115
Interest cost	1,268	883	806
Actuarial loss/(gain)	(2,645)	(9,360)
Implicit rate subsidy	(237)	(236)
Plan participants contributions	179	207
Administrative expenses paid	0	0
Benefits paid and settlements	(769)	(1,108)
Benefit obligation at end of year	24,264	25,830	34,412
Change in plan assets
Fair value of assets at beginning of year	17,952	21,767
Actual return on plan assets	3,136	(3,606)
Employer contributions	920	626
Plan participants contributions	179	207
Administrative expenses paid	(67)	(65)
Benefits paid and settlements	(913)	(977)
Fair value of plan assets at end of year	21,207	17,952	$ 21,767
Funded status at end of year	$ (3,057)	$ (7,878)