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Supplemental Balance Sheet Information - Schedule of Supplemental Balance Sheet Information (Parenthetical) (Details) - USD ($) $ in Millions | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2020 | Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract] |  |
Excess of Replacement or Current Costs over Stated LIFO Value |  | $ 11.9
Excess of stated LIFO value over replacement or current costs | $ 4.2 |
Construction in progress temporarily idled | $ 19.9 |
Workers' Compensation Discount, Percent | 0.50% | 1.75%
Workers compensation liability | $ 29.5 | $ 26.6
Unpaid claim liabilities relating to insurance recoverables | $ 30.4 | $ 29.2

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