Retirement Benefit Plans (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	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	$ 380	$ 384	$ 846	$ 797
Interest Cost	595	519	1,120	1,049
Expected Return on Plan Assets	(923)	(851)	(1,855)	(1,708)
Amortization of Prior Service Cost	33	15	66	31
Amortization of Net Loss (Gain)	0	23	0	59
Net Periodic Benefit Cost	85	90	177	228
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	22	122	39	285
Interest Cost	2	97	160	159
Expected Return on Plan Assets	0	0	0	0
Amortization of Prior Service Cost	10	10	20	20
Amortization of Net Loss (Gain)	(9)	19	12	37
Net Periodic Benefit Cost	25	248	231	501
Plan Contributions During the Period	128	110	255	226
Estimated Future Contributions in the Current Fiscal Year	255		255
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	8	10	23	28
Interest Cost	79	80	160	167
Expected Return on Plan Assets	0	0	0	0
Amortization of Prior Service Cost	25	26	51	52
Amortization of Net Loss (Gain)	(82)	(98)	(169)	(177)
Net Periodic Benefit Cost	30	18	65	70
Plan Contributions During the Period	54	$ 20	81	$ 47
Estimated Future Contributions in the Current Fiscal Year	$ 81		$ 81
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%