Pension and Other Post-Retirement Benefit Plans - Net Funded Status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plans
Change in benefit obligation
Obligation, beginning balance	$ 648,242	$ 839,267
Service cost	0	0	$ 0
Interest cost	34,526	24,173	22,387
Special termination benefits	0	0
Plan amendment	0	0
Plan transfers	2,276	2,386
Return of excess premiums	0	0
Benefits paid	(39,643)	(37,998)
Settlement payments	(139,605)	0
Settlements	(139,605)	0
Actuarial (gain) loss	16,163	(179,586)
Obligation, ending balance	521,959	648,242	839,267
Change in plan assets
Actual (loss) gain on plan assets	72,006	(188,855)
Employer contributions	1,310	1,304
Funded status
Funded status	20,526	13,194
Pension Plans | Fair Value, Recurring
Change in plan assets
Plan assets, beginning balance	627,032	850,195
Plan assets, ending balance	523,376	627,032	850,195
Pension Plans | Current liabilities
Funded status
Funded status	(1,380)	(1,343)
Pension Plans | Non-current liabilities
Funded status
Funded status	(17,731)	(33,063)
Post-retirement Healthcare Plans
Change in benefit obligation
Obligation, beginning balance	2,672	3,142
Service cost	53	76	95
Interest cost	132	59	42
Special termination benefits	0	0
Plan amendment	0	0
Plan transfers	0	0
Return of excess premiums	0	0
Benefits paid	(306)	(308)
Settlement payments	0	0
Settlements	0	0
Actuarial (gain) loss	(594)	(297)
Obligation, ending balance	1,957	2,672	3,142
Change in plan assets
Actual (loss) gain on plan assets	0	0
Employer contributions	306	308
Funded status
Funded status	0	0
Post-retirement Healthcare Plans | Fair Value, Recurring
Change in plan assets
Plan assets, beginning balance	0	0
Plan assets, ending balance	0	0	$ 0
Post-retirement Healthcare Plans | Current liabilities
Funded status
Funded status	(319)	(401)
Post-retirement Healthcare Plans | Non-current liabilities
Funded status
Funded status	$ (1,638)	$ (2,271)