Cost Reduction and Asset Actions (Carrying Amount of Accrual) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2017		Jun. 30, 2017	[1]	Mar. 31, 2017	[1]	Dec. 31, 2016	[1]	Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Cost reduction and asset actions	$ 48.4	[1]	$ 42.7		$ 10.3		$ 50.0		$ 0.0	$ 151.4	[1]	$ 34.5
Cost Reduction Actions
Restructuring Cost and Reserve [Line Items]
Cost reduction and asset actions										154.8		34.5
Noncash expenses										(84.2)
Cash expenditures									(31.2)	(36.9)		(21.6)
Amount reflected in pension liability									(0.4)	(2.0)		(0.9)
Amount reflected in other noncurrent liabilities										(2.2)
Currency translation adjustment										(0.3)		0.3
Accrued Balance	41.5								9.9	41.5		12.3
Cost Reduction Actions | Severance and Other Benefits
Restructuring Cost and Reserve [Line Items]
Cost reduction and asset actions										66.3		34.5
Noncash expenses										0.0
Cash expenditures									(30.3)	(35.7)		(21.6)
Amount reflected in pension liability									(0.4)	(2.0)		(0.9)
Amount reflected in other noncurrent liabilities										0.0
Currency translation adjustment										(0.3)		0.3
Accrued Balance	40.6								9.9	40.6		12.3
Cost Reduction Actions | Asset Actions/Other
Restructuring Cost and Reserve [Line Items]
Cost reduction and asset actions										88.5		0.0
Noncash expenses										(84.2)
Cash expenditures									(0.9)	(1.2)		0.0
Amount reflected in pension liability									0.0	0.0		0.0
Amount reflected in other noncurrent liabilities										(2.2)
Currency translation adjustment										0.0		0.0
Accrued Balance	$ 0.9								$ 0.0	$ 0.9		$ 0.0

[1] For additional information, refer to Note 5, Cost Reduction and Asset Actions.