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Retirement Benefit Plans (Details) - USD ($) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2020 | Mar. 31, 2019 | Dec. 31, 2019
Net Periodic Benefit Cost [Line Items] |  |  |
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 |  |  | 2.04%
Service Cost | $ 430 | $ 399 |
Interest Cost | 417 | 397 |
Expected Return on Plan Assets | (904) | (770) |
Amortization of Prior Service (Credit) Cost | 16 | 17 |
Amortization of Net Loss | 1 | 153 |
Net Periodic Cost | (40) | 196 |
Plan Contributions During the Period | 0 | 0 |
Select Executive Retirement Plan |  |  |
Net Periodic Benefit Cost [Line Items] |  |  |
Assumptions used calculating benefit obligation, interest rate to annuitize cash balance account |  |  | 3.09%
Service Cost | 103 | 97 |
Interest Cost | 54 | 52 |
Expected Return on Plan Assets | 0 | 0 |
Amortization of Prior Service (Credit) Cost | 11 | 14 |
Amortization of Net Loss | 33 | 27 |
Net Periodic Cost | 201 | 190 |
Plan Contributions During the Period | 117 | 116 |
Post-Retirement Benefit Plans |  |  |
Net Periodic Benefit Cost [Line Items] |  |  |
Assumptions used calculating benefit obligation, interest rate to annuitize cash balance account |  |  | 3.68%
Service Cost | 33 | 30 |
Interest Cost | 78 | 89 |
Expected Return on Plan Assets | 0 | 0 |
Amortization of Prior Service (Credit) Cost | 27 | 25 |
Amortization of Net Loss | 2 | (17) |
Net Periodic Cost | 140 | 127 |
Plan Contributions During the Period | $ 78 | $ 37 |
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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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details
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