Retirement Benefits - Change in Net Benefit Obligation and Fair Value (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Other Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	$ 11,654	$ 12,114
Amendments	38	205
Service cost	217	155
Interest cost	311	302
Actuarial loss (gain)	2,397	514
Benefits paid	808	803
Medicare part D subsidy received	0	195
Administrative expense	0	0
Benefit obligation at end of period	9,015	11,654
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of period	6,341	5,918
Actual return on plan assets	(550)	1,005
Employer contribution	207	222
Benefits paid	(808)	(804)
Administrative expense	0	0
Fair value of plan assets at end of period	5,190	6,341
Funded status at end of period	(3,825)	(5,313)
Nonqualified Plan | Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	43,155	46,742
Amendments	0	0
Service cost	557	456
Interest cost	1,253	1,183
Actuarial loss (gain)	5,260	(828)
Benefits paid	7,659	6,054
Medicare part D subsidy received	0	0
Administrative expense	0	0
Benefit obligation at end of period	32,046	43,155
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of period	0	0
Actual return on plan assets	0	0
Employer contribution	7,659	6,054
Benefits paid	(7,659)	(6,054)
Administrative expense	0	0
Fair value of plan assets at end of period	0	0
Funded status at end of period	(32,046)	(43,155)
Qualified Plan | Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	834,960	849,383
Amendments	0	0
Service cost	26,351	26,888
Interest cost	24,263	22,381
Actuarial loss (gain)	215,005	6,826
Benefits paid	80,226	55,831
Medicare part D subsidy received	0	0
Administrative expense	(1,065)	(1,035)
Benefit obligation at end of period	589,278	834,960
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of period	898,550	834,655
Actual return on plan assets	(176,537)	102,787
Employer contribution	18,000	18,000
Benefits paid	(80,226)	(55,831)
Administrative expense	(1,254)	(1,061)
Fair value of plan assets at end of period	658,533	898,550
Funded status at end of period	$ 69,255	$ 63,590