Quarterly Results - Unaudited - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Captive Insurance Equity Affiliate [Member]
Quarterly Charges And Credits	$ 1.1	$ 0.4	$ 0.4	$ 0.6	$ 0.7	$ 0.6	$ 0.3	$ 0.1
Currency Conversion [Member]
Quarterly Charges And Credits	0.1	0.1	0.3					$ 0.1
Cost Streamlining Initiative [Member]
Quarterly Charges And Credits				0.3
Restructuring Charges (Credits) [Member]
Quarterly Charges And Credits					(0.4)
Houghton Combination-related expenses [Member]
Quarterly Charges And Credits	7.7	$ 9.7	4.3	$ 9.1	$ 0.4	$ 1.2
U.S. Pension Plan Settlement Charge [Member]
Quarterly Charges And Credits			$ 1.9
U.S. Tax Reform Charges [Member]
Quarterly Charges And Credits	22.2
Loss On Disposal Of Held For Sale Asset [Member]
Quarterly Charges And Credits	0.1
Insurance Insolvency Recovery [Member]
Quarterly Charges And Credits	$ 0.6