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Retirement Benefit Plans (Details) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2021 USD ($) | Sep. 30, 2020 USD ($) | Sep. 30, 2021 USD ($) | Sep. 30, 2020 USD ($) | Dec. 31, 2020
Net Periodic Benefit Cost [Line Items] |  |  |  |  |
Interest credit under cash balance plan |  |  | 0.03 |  |
Employer matching contribution, percentage |  |  | 5.00% |  |
Employees' Pension Plan |  |  |  |  |
Net Periodic Benefit Cost [Line Items] |  |  |  |  |
Assumptions used calculating benefit obligation, interest rate to annuitize cash balance account |  |  |  |  | 0.53%
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 | $ 484,000 | $ 416,000 | $ 1,451,000 | $ 1,247,000 |
Interest Cost | 340,000 | 387,000 | 1,023,000 | 1,159,000 |
Expected Return on Plan Assets | (945,000) | (902,000) | (2,835,000) | (2,706,000) |
Amortization of Prior Service (Credit) Cost | 20,000 | 15,000 | 59,000 | 47,000 |
Amortization of Net Loss (Gain) | 0 | 20,000 | 0 | 61,000 |
Net Periodic (Benefit) Cost | (101,000) | (64,000) | (302,000) | (192,000) |
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 |  |  |  |  | 2.31%
Defined benefit plan, amortization of service cost |  |  | 12 years 6 months |  |
Defined benefit plan, benefit obligation, period increase (decrease) |  |  | $ 122,797 |  |
Service Cost | 146,000 | 102,000 | 437,000 | 306,000 |
Interest Cost | 48,000 | 48,000 | 143,000 | 144,000 |
Expected Return on Plan Assets | 0 | 0 | 0 | 0 |
Amortization of Prior Service (Credit) Cost | 12,000 | 11,000 | 36,000 | 32,000 |
Amortization of Net Loss (Gain) | 44,000 | 37,000 | 134,000 | 110,000 |
Net Periodic (Benefit) Cost | 250,000 | 198,000 | 750,000 | 592,000 |
Plan Contributions During the Period | 118,000 | 116,000 | 354,000 | 349,000 |
Estimated Future Contributions in the Current Fiscal Year | 118,000 |  | 118,000 |  |
Post-Retirement Benefit Plans |  |  |  |  |
Net Periodic Benefit Cost [Line Items] |  |  |  |  |
Assumptions used calculating benefit obligation, interest rate to annuitize cash balance account |  |  |  |  | 3.09%
Service Cost | 27,000 | 30,000 | 82,000 | 92,000 |
Interest Cost | 62,000 | 78,000 | 186,000 | 233,000 |
Expected Return on Plan Assets | 0 | 0 | 0 | 0 |
Amortization of Prior Service (Credit) Cost | 27,000 | 27,000 | 80,000 | 80,000 |
Amortization of Net Loss (Gain) | (22,000) | 0 | (66,000) | 0 |
Net Periodic (Benefit) Cost | 94,000 | 135,000 | 282,000 | 405,000 |
Plan Contributions During the Period | 32,000 | $ 54,000 | 87,000 | $ 191,000 |
Estimated Future Contributions in the Current Fiscal Year | $ 32,000 |  | $ 32,000 |  |
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% |  |

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