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Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 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 | $ 9 | $ 9 | $ 19 | $ 17 |
Interest cost | 31 | 36 | 62 | 73 |
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 | (8) |
Net Periodic Benefit Cost | 40 | 41 | 81 | 82 |
Defined Benefit Plan, Plan Assets, Contributions by Employer |  |  | 119 |  |
Pension Plan [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Service cost | 325 | 304 | 650 | 609 |
Interest cost | 779 | 866 | 1,558 | 1,733 |
Expected return on plan assets | (1,049) | (896) | (2,099) | (1,793) |
Defined Benefit Plan, Amortization of Prior Service Cost (Credit) | 0 | 0 | 0 | 0 |
Net amortization of net (gain) loss | 492 | 390 | 984 | 779 |
Net Periodic Benefit Cost | $ 547 | $ 664 | 1,093 | $ 1,328 |
Defined Benefit Plan, Plan Assets, Contributions by Employer |  |  | $ 1,200 |  |

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