Retirement Benefit Plans (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Interest credit under cash balance plan			0.03
Employer matching contribution, percent of match, maximum			5.00%
Defined benefit plan, service cost and interest cost					$ 3,300
Defined benefit plan, unamortized net loss					$ 7,200
Defined benefit plan, benefit obligation from lump sum payment to total benefit obligation ratio (in percent)					8.06%
Defined benefit plan, net periodic benefit cost, loss due to settlement					$ 577
Employees' Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Assumptions used calculating benefit obligation, interest rate to annuitize cash balance account						5.50%
Defined benefit plan, increase in benefit payable (in percent)	3.00%		3.00%
Defined benefit plan, benefit obligation, increase (decrease) for plan amendment			$ 351,638
Defined benefit plan, amortization of service cost (in years)			9 years 8 months 12 days
Net Periodic Benefit Cost
Service Cost	$ 423	$ 398	$ 1,269	$ 1,195
Interest Cost (Benefit)	562
Interest Cost		524	1,682	1,573
Expected Return on Plan Assets	(928)	(854)	(2,783)	(2,562)
Amortization of Prior Service Cost	32	16	98	47
Amortization of Net Loss (Gain)	0	30	0	89
Net Periodic Benefit Cost	89	114	266	342
Plan Contributions During the Period	0	0	0	0
Estimated Future Contributions in the Current Fiscal Year	0		$ 0
Select Executive Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Assumptions used calculating benefit obligation, interest rate to annuitize cash balance account						5.76%
Defined benefit plan, amortization of service cost (in years)			12 years 6 months
Defined benefit plan, benefit obligation, period increase (decrease)			$ 122,797
Net Periodic Benefit Cost
Service Cost	20	143	59	428
Interest Cost (Benefit)	(157)
Interest Cost		85	3	244
Expected Return on Plan Assets	237	0	237	0
Amortization of Prior Service Cost	9	9	29	29
Amortization of Net Loss (Gain)	6	18	18	55
Net Periodic Benefit Cost	115	255	346	756
Plan Contributions During the Period	127	99	382	325
Estimated Future Contributions in the Current Fiscal Year	127		127
Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Assumptions used calculating benefit obligation, interest rate to annuitize cash balance account						5.83%
Net Periodic Benefit Cost
Service Cost	11	14	34	42
Interest Cost (Benefit)	79
Interest Cost		82	239	249
Expected Return on Plan Assets	0	0	0	0
Amortization of Prior Service Cost	26	26	77	78
Amortization of Net Loss (Gain)	(84)	(88)	(253)	(265)
Net Periodic Benefit Cost	32	34	97	104
Plan Contributions During the Period	31	$ 28	112	$ 75
Estimated Future Contributions in the Current Fiscal Year	$ 37		$ 37
On or Subsequent to January 1, 2003
Defined Benefit Plan Disclosure [Line Items]
Service credits, percent of eligible salaries			6.00%
Prior to January 1, 2003 | Minimum
Defined Benefit Plan Disclosure [Line Items]
Service credits, percent of eligible salaries			6.00%
Prior to January 1, 2003 | Maximum
Defined Benefit Plan Disclosure [Line Items]
Service credits, percent of eligible salaries			12.00%