Significant accounting policies [Line Items]

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- Definition

Workers Compensation Liability, Undiscounted

+ References

No definition available.

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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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Carrying value as of the balance sheet date of obligations, excluding pension and other postretirement benefits, incurred through that date and payable for perquisites provided to employees pertaining to services received from them.

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- Definition

Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.

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- Definition

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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- Definition

Amount of interest capitalized during the period.

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

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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

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Summary of Significant Accounting Policies, Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Jan. 01, 2018
Significant accounting policies
Excess of current cost over the stated LIFO value of inventory	$ 42.9		$ 42.9		$ 24.3
Interest expense capitalized	0.4	$ 0.7	1.3	$ 1.9
Workers compensation liability	27.9		$ 27.9		$ 24.8
Workers' compensation accrual, discount rate (percent)			3.00%		2.25%
Accrued liabilities for employee healthcare benefits	$ 3.1		$ 3.1		$ 3.5
Shares available for award (shares)	577,300		577,300
Retained earnings	$ 135.6		$ 135.6		$ 85.5	$ 95.6
Accrued salaries, wages and related expenses
Significant accounting policies
Accrued salaries, wages and related expenses	10.6		10.6
Accounting Standards Update 2016-01
Significant accounting policies
Retained earnings						0.4
Tax impact						0.2
Difference between Revenue Guidance in Effect before and after Topic 606 \| Accounting Standards Update 2014-09
Significant accounting policies
Retained earnings	$ (13.7)		$ (13.7)			10.1
Tax impact						$ 3.3