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Basis of Presentation and Recent Accounting Pronouncements, Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2020 | Mar. 31, 2019 | Dec. 31, 2019
Significant accounting policies |  |  |
Operating lease assets | $ 28.8 |  | $ 25.8
Operating lease liabilities, current | 4.5 |  | 3.9
Excess of Replacement or Current Costs over Stated LIFO Value | 1.9 |  | 11.9
Interest expense capitalized | 0.3 | $ 0.5 |
Workers compensation liability | $ 29.0 |  | $ 29.2
Workers' Compensation Discount, Percent | 1.00% |  | 1.75%
Shares available for awards (shares) | 380,201 |  |
Retained earnings | $ 190.6 |  | $ 172.8
Long-term portion of operating lease liabilities | 27.8 |  | $ 25.2
Accrued salaries, wages and related expenses |  |  |
Significant accounting policies |  |  |
Accrued salaries, wages and related expenses | $ 3.7 |  |

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