Summary of Significant Accounting Policies, Narrative (Details) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Accounting policies additional disclosures
Number of operating segments | segment					1
Non-cash impairment charges					$ 0.1	$ 1.5	$ 0.0
Advertising costs					1.2	0.6	1.3
Research and development costs					9.5	8.9	7.8
Lower of cost or market inventory write-down	$ 2.6	$ 0.0	$ 0.0	$ 0.0	2.6	0.0	$ 0.0
Excess of current cost over the stated LIFO value of inventory	(24.1)				(24.1)	37.6
Impairment of the carrying value of goodwill	0.0				0.0	0.0
Undiscounted workers' compensation liabilities	23.5				$ 23.5	$ 25.9
Discount rate used in estimating liabilities for worker compensation claims					1.75%	1.75%
Accrued employee healthcare benefits	3.2				$ 3.2	$ 2.9
Margin deposits with counterparties	0.0				0.0	$ 0.0
Customer deposits, current	$ 0.9				$ 0.9
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
Number of days to maturity for debt investment securities to be classified as cash and cash equivalents					90 days
Period over which accounts receivable is due, days					60 days