Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions		3 Months Ended								12 Months Ended
	Jan. 01, 2018 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) customer segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Line of Credit Facility [Line Items]
Number of reportable segments | segment										3
Allowance for doubtful accounts		$ 6.2				$ 4.5				$ 6.2	$ 4.5
Sale of accounts receivable										106.8	80.0
Income (expense) related to discount on sale of accounts receivable										$ (1.0)	(0.6)
Number of customers with uncollateralized accounts receivable in automotive industry | customer										6
Uncollateralized accounts receivable		$ 46.8								$ 46.8
Percentage of accounts receivable uncollateralized										18.00%
Revenue from sales to major customers										$ 338.2
Percentage of revenue from sales to major customers		20.00%								20.00%
Net sales		$ 405.9	$ 414.3	$ 432.2	$ 405.7	366.0	$ 352.2	$ 350.9	$ 343.8	$ 1,658.1	1,412.9	$ 1,276.9
Retained earnings		$ 265.9				$ 216.1				$ 265.9	$ 216.1
Building | Minimum
Line of Credit Facility [Line Items]
Property, plant and equipment, useful life										5 years
Building | Maximum
Line of Credit Facility [Line Items]
Property, plant and equipment, useful life										40 years
Machinery and Equipment
Line of Credit Facility [Line Items]
Property, plant and equipment, useful life, majority range, minimum										3 years
Property, plant and equipment, useful life, majority range, maximum										10 years
Machinery and Equipment | Minimum
Line of Credit Facility [Line Items]
Property, plant and equipment, useful life										1 year
Machinery and Equipment | Maximum
Line of Credit Facility [Line Items]
Property, plant and equipment, useful life										20 years
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Line of Credit Facility [Line Items]
Net sales	$ 13.6
Retained earnings	$ 2.6