Business Restructuring and Cost Reduction 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, 2016		Jun. 30, 2016	[1]	Mar. 31, 2016	[1]	Dec. 31, 2015	[1]	Sep. 30, 2014	Sep. 30, 2017		Sep. 30, 2016		Sep. 30, 2015	Sep. 30, 2014
Restructuring Cost and Reserve [Line Items]
Business restructuring and cost reduction actions	$ 48.4	[1]	$ 42.7		$ 10.3		$ 50.0		$ 10.6	[1]	$ 13.2		$ 10.7		$ 0.0			$ 151.4	[1]	$ 34.5	[1]	$ 180.1
Cost Reduction Actions
Restructuring Cost and Reserve [Line Items]
Business restructuring and cost reduction actions																		154.8		34.5
Noncash expenses																		(84.2)
Amount reflected in pension liability																		(2.0)		(0.9)
Amount reflected in other noncurrent liabilities																		(2.2)
Cash expenditures																		(36.9)		(21.6)
Currency translation adjustment																		(0.3)		0.3
Accrued Balance	41.5								12.3									41.5		12.3
Cost Reduction Actions | Severance and Other Benefits
Restructuring Cost and Reserve [Line Items]
Business restructuring and cost reduction actions																		66.3		34.5
Noncash expenses																		0.0
Amount reflected in pension liability																		(2.0)		(0.9)
Amount reflected in other noncurrent liabilities																		0.0
Cash expenditures																		(35.7)		(21.6)
Currency translation adjustment																		(0.3)		0.3
Accrued Balance	40.6								12.3									40.6		12.3
Cost Reduction Actions | Asset Actions/Other
Restructuring Cost and Reserve [Line Items]
Business restructuring and cost reduction actions																		88.5		0.0
Noncash expenses																		(84.2)
Amount reflected in pension liability																		0.0		0.0
Amount reflected in other noncurrent liabilities																		(2.2)
Cash expenditures																		(1.2)		0.0
Currency translation adjustment																		0.0		0.0
Accrued Balance	0.9								0.0									0.9		0.0
Business Realignment and Reorganization
Restructuring Cost and Reserve [Line Items]
Business restructuring and cost reduction actions																						180.1	$ 11.1
Noncash expenses																						(40.2)
Amount reflected in pension liability																						(11.2)
Cash expenditures																				(32.4)		(101.5)	(1.7)
Currency translation adjustment																				(0.4)		(0.4)
Favorable restructuring reserve settlement																		(3.4)
Accrued Balance	0.0								3.4								$ 9.4	0.0		3.4		36.2	9.4
Business Realignment and Reorganization | Severance and Other Benefits
Restructuring Cost and Reserve [Line Items]
Business restructuring and cost reduction actions																	11.1					131.5	11.1
Noncash expenses																						0.0
Amount reflected in pension liability																						(11.2)
Cash expenditures																				(28.6)		(100.3)	(1.7)
Currency translation adjustment																				(0.4)		(0.4)
Favorable restructuring reserve settlement																		0.0
Accrued Balance	0.0								0.0								9.4	0.0		0.0		29.0	9.4
Business Realignment and Reorganization | Asset Actions/Other
Restructuring Cost and Reserve [Line Items]
Business restructuring and cost reduction actions																						48.6	0.0
Noncash expenses																						(40.2)
Amount reflected in pension liability																						0.0
Cash expenditures																				(3.8)		(1.2)	0.0
Currency translation adjustment																				0.0		0.0
Favorable restructuring reserve settlement																		(3.4)
Accrued Balance	$ 0.0								$ 3.4								$ 0.0	$ 0.0		$ 3.4		$ 7.2	$ 0.0

[1] For additional information, see Note 5, Business Restructuring and Cost Reduction Actions.