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

Significant accounting policies [Line Items]

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- Definition

Workers Compensation Liability, Undiscounted

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Carrying value as of the balance sheet date of obligations incurred and payable for incentive compensation awarded to employees and directors or earned by them based on the terms of one or more relevant arrangements.

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The excess of replacement or current cost over the stated LIFO (last in first out) inventory value when the LIFO inventory method is utilized.

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Amount of interest capitalized during the period.

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Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

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Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent.

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Amount of lessee's right to use underlying asset under operating lease.

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The cumulative amount of the reporting entity's undistributed earnings or deficit.

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Percent discount applied to worker's compensation reserve liability to reduce the reserve to present value.

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