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Employee Benefit Plans, 401(k) Plan and Other Retirement Benefits (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Other Retirement Benefits [Abstract] |  |  |
Supplemental retirement benefits for retired executives under other retirement benefits plan | $ 1.6 | $ 1.7 |
Expense related to other retirement benefits plan | 0.2 | 0.1 | $ 0.1
401(K) Plan [Member] |  |  |
Defined benefit plan disclosure [Abstract] |  |  |
Employer contribution to plan | $ 3.6 | $ 3.6 | $ 3.2

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