Pension and Other Postretirement Benefit Plans (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) plan	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Fixed Income Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	100.00%	100.00%
Directors' Plan [Member]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 68,000	$ 144,000
Deferred Compensation Plan, Amounts Held in Rabbi Trust	2,000,000.0	1,900,000
Defined Benefit Plan, Annual Retirement Benefit	$ 48,000
Defined Benefit Contributions, Months of Benefit Used in Lump Sum Payment in the Event of Termination	120 months
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 124,000	$ 104,000
Number of Unfunded Postretirement Benefit Plans | plan	2
Full Time Employment, Years of Service	5 years
Cost Sharing Arrangement, Medical Benefits Percentage	50.00%
Medical Premiums, Required Percentage to Be Paid By Spouses of Future Retirees	100.00%
Retirement Plan [Member]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	4.75%	4.25%	4.75%
Retirement Plan [Member] | Savings Bank [Member]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	$ 0
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 0	$ 0	$ 0
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	4.75%
Retirement Plan [Member] | Minimum
Defined Benefit Plan, Benefit Service Period	3 years
Retirement Plan [Member] | Minimum | Fixed Income Securities [Member] | Savings Bank [Member]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	3.00%
Retirement Plan [Member] | Maximum
Defined Benefit Plan, Benefit Service Period	10 years
Retirement Plan [Member] | Maximum | Fixed Income Securities [Member] | Savings Bank [Member]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	5.00%
Defined Contribution Retirement Plan ("DCRP") [Member] | Savings Bank [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	4.00%
Non-qualified Deferred Compensation Plan [Member]
Defined Contribution Plan, Annual Employer Matching of Employees Contribution, Percent	50.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	5.00%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	20.00%
Defined Contribution Plan, Employer's Matching Contribution, Vesting Percentage, Upon Change of Control	100.00%
Defined Contribution Plan, Cost	$ 500,000	500,000	500,000
Defined Contribution Plan, Service Period Requirement	1 year
Defined Contribution Plan, Vesting Period	5 years
Deferred Compensation Plan, Amounts Held in Rabbi Trust	$ 18,900,000	16,400,000
The 401K Plan [Member]
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	20.00%
Defined Contribution Plan, Employer's Matching Contribution, Vesting Percentage, Upon Change of Control	100.00%
Defined Contribution Plan, Cost	$ 3,400,000	$ 4,700,000	$ 7,400,000
Defined Contribution Plan, Service Period Requirement	1 year
Defined Contribution Plan, Vesting Period	5 years
The 401K Plan [Member] | Savings Bank [Member]
Defined Contribution Plan, Annual Employer Matching of Employees Contribution, Percent	50.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	3.00%