Contingent Liability Contingent Liability (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Losses, Low Estimate	$ 1.4
Environmental Exit Costs, Liability for Remediation	1.4	$ 1.0
Environmental Remediation Expense	0.5
Minimum [Member]
Loss Contingencies [Line Items]
Environmental Exit Costs, Anticipated Cost	0.9
Maximum [Member]
Loss Contingencies [Line Items]
Environmental Exit Costs, Anticipated Cost	$ 2.0