Cost Reduction and Asset Actions (Carrying Amount of Accrual) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Cost reduction and asset actions	$ 0.0	$ 50.0	$ 151.4
Cost Reduction Actions
Restructuring Cost and Reserve [Line Items]
Cost reduction and asset actions			154.8
Noncash expenses			(84.2)
Amount reflected in pension liability			(2.0)
Amount reflected in other noncurrent liabilities			(2.2)
Cash expenditures	(13.6)		(36.9)
Currency translation adjustment	0.2		(0.3)
Accrued balance	28.1		41.5	$ 12.3
Cost Reduction Actions | Severance And Other Benefits
Restructuring Cost and Reserve [Line Items]
Cost reduction and asset actions			66.3
Noncash expenses			0.0
Amount reflected in pension liability			(2.0)
Amount reflected in other noncurrent liabilities			0.0
Cash expenditures	(13.5)		(35.7)
Currency translation adjustment	0.2		(0.3)
Accrued balance	27.3		40.6	12.3
Cost Reduction Actions | Asset Actions/Other
Restructuring Cost and Reserve [Line Items]
Cost reduction and asset actions			88.5
Noncash expenses			(84.2)
Amount reflected in pension liability			0.0
Amount reflected in other noncurrent liabilities			(2.2)
Cash expenditures	(0.1)		(1.2)
Currency translation adjustment	0.0		0.0
Accrued balance	$ 0.8		$ 0.9	$ 0.0