Retirement Benefit Plans (Details)	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Net Periodic Benefit Cost [Line Items]
Interest credit under cash balance plan				0.03
Employer matching contribution, percentage				5.00%
Service cost and interest cost						$ 3,300,000
Unamortized net loss						$ 7,200,000
Benefit obligation from lump sum payment to total benefit obligation ratio						8.06%
Defined benefit plan, net periodic benefit cost, loss due to settlement		$ 577,000
Employees' Pension Plan
Net Periodic Benefit Cost [Line Items]
Assumptions used calculating benefit obligation, interest rate to annuitize cash balance account						5.09%
Defined benefit plan, increase in benefit payable, percent	3.00%			3.00%
Defined benefit plan, benefit obligation, increase (decrease) for plan amendment				$ 351,638
Defined benefit plan, amortization of service cost				9 years 8 months 12 days
Service Cost	$ 398,000		$ 469,000	$ 1,195,000	$ 1,408,000
Interest Cost	524,000		360,000	1,573,000	1,079,000
Expected Return on Plan Assets	(854,000)		(1,078,000)	(2,562,000)	(3,235,000)
Amortization of Prior Service Cost	16,000		19,000	47,000	58,000
Amortization of Net Loss (Gain)	30,000		550,000	89,000	550,000
Net Periodic Cost	114,000		320,000	342,000	(140,000)
Plan Contributions During the Period	0		0	0	0
Estimated Future Contributions in the Current Fiscal Year	0			$ 0
Select Executive Retirement Plan
Net Periodic Benefit Cost [Line Items]
Assumptions used calculating benefit obligation, interest rate to annuitize cash balance account						5.60%
Defined benefit plan, amortization of service cost				12 years 6 months
Defined benefit plan, benefit obligation, period increase (decrease)				$ 122,797
Service Cost	143,000		208,000	428,000	626,000
Interest Cost	85,000		57,000	244,000	169,000
Expected Return on Plan Assets	0		0	0	0
Amortization of Prior Service Cost	9,000		11,000	29,000	33,000
Amortization of Net Loss (Gain)	18,000		53,000	55,000	159,000
Net Periodic Cost	255,000		329,000	756,000	987,000
Plan Contributions During the Period	99,000		116,000	325,000	347,000
Estimated Future Contributions in the Current Fiscal Year	108,000			108,000
Post-Retirement Benefit Plans
Net Periodic Benefit Cost [Line Items]
Assumptions used calculating benefit obligation, interest rate to annuitize cash balance account						5.41%
Service Cost	14,000		23,000	42,000	68,000
Interest Cost	82,000		61,000	249,000	185,000
Expected Return on Plan Assets	0		0	0	0
Amortization of Prior Service Cost	26,000		27,000	78,000	80,000
Amortization of Net Loss (Gain)	(88,000)		(39,000)	(265,000)	(117,000)
Net Periodic Cost	34,000		72,000	104,000	216,000
Plan Contributions During the Period	28,000		$ 43,000	75,000	$ 131,000
Estimated Future Contributions in the Current Fiscal Year	$ 25,000			$ 25,000
On or Subsequent to January 1, 2003
Net Periodic Benefit Cost [Line Items]
Service credits, percent of eligible salaries				6.00%
Minimum | Prior to January 1, 2003
Net Periodic Benefit Cost [Line Items]
Service credits, percent of eligible salaries				6.00%
Maximum | Prior to January 1, 2003
Net Periodic Benefit Cost [Line Items]
Service credits, percent of eligible salaries				12.00%