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Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019 | Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year |  |  |  |  | $ 3,700
Post-Retirement Health Benefits [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year |  |  |  |  | $ 251
Service cost | $ 10 | $ 9 | $ 29 | $ 26 |
Interest cost | 32 | 36 | 94 | 109 |
Expected return on plan assets | 0 | 0 | 0 | 0 |
Defined Benefit Plan, Amortization of Prior Service Cost (Credit) | 0 | 0 | 0 | 0 |
Net amortization of net (gain) loss | 0 | (4) | 0 | (12) |
Net Periodic Benefit Cost | 42 | 41 | 123 | 123 |
Defined Benefit Plan, Plan Assets, Contributions by Employer |  |  | 176 |  |
Pension Plan [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Service cost | 325 | 304 | 975 | 913 |
Interest cost | 779 | 866 | 2,337 | 2,599 |
Expected return on plan assets | (1,050) | (896) | (3,149) | (2,689) |
Defined Benefit Plan, Amortization of Prior Service Cost (Credit) | 1 | 0 | 1 | 1 |
Net amortization of net (gain) loss | 492 | 389 | 1,476 | 1,168 |
Net Periodic Benefit Cost | $ 547 | $ 663 | 1,640 | $ 1,992 |
Defined Benefit Plan, Plan Assets, Contributions by Employer |  |  | $ 3,000 |  |

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