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Employee Benefit Plans - Postretirement Healthcare Plan (Details) - Postretirement Healthcare Plan - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits |  |  |
Defined Benefit Plan, Funded (Unfunded) Status of Plan | $ 0.3 | $ 0.4 |
Minimum age requirement | 55 years |  |
Requisite service period | 15 years |  |
Net periodic benefit cost | $ 0.5 | $ 0.7 | $ 0.8

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