Summary of Significant Accounting Policies, Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)	Jan. 01, 2018 USD ($)	[1]	Jan. 01, 2017 USD ($)
Accounting policies additional disclosures
Effect of LIFO Inventory Liquidation on Income	$ 3.6
Number of operating segments | segment	1
Advertising costs	$ 0.4	$ 0.3	$ 0.7
Research and development costs	10.5	9.8	10.0
Excess of current cost over the stated LIFO value of inventory	11.9	31.7
Non-cash asset impairment charges	26.1	1.4	$ 19.2
Undiscounted workers' compensation liabilities	$ 29.2	$ 27.6
Discount rate used in estimating liabilities for worker compensation claims	1.75%	3.00%
Accrued employee healthcare benefits	$ 3.5	$ 3.6
Retained earnings	172.8	150.2
Operating lease assets	25.8	0.0
Operating Lease, Liability, Current	3.9
Long-term portion of operating lease liabilities	$ 25.2	$ 0.0
Cumulative-effect adjustment					$ 10.3		$ 0.3
Minimum
Accounting policies additional disclosures
Period over which accounts receivable is due, days	30 days
Number of days in maturity for debt investment securities to be classified as short-term investments	90 days
Maximum
Accounting policies additional disclosures
Period over which accounts receivable is due, days	90 days
Number of days to maturity for debt investment securities to be classified as cash and cash equivalents	90 days
Accounting Standards Update 2016-02
Accounting policies additional disclosures
Operating lease assets				$ 29.0
Operating Lease, Liability, Current				4.1
Long-term portion of operating lease liabilities				27.4
Cumulative-effect adjustment				$ 0.0

[1] Cumulative-effect adjustment relates to our adoption of ASC 606 and ASU 2016-01 (each as defined in Note 1).