Goodwill and Other Intangible Assets - Changes in Carrying amount of Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Goodwill
Beginning balance	$ 1,077.7	$ 1,073.9
Acquisition of businesses	6.8	0.8
Divestiture of business (Note 13)		(10.3)
Translation	(9.0)	13.3
Ending balance	1,075.5	1,077.7
Architecture & Software
Goodwill
Beginning balance	417.2	414.5
Acquisition of businesses	6.8	0.0
Divestiture of business (Note 13)		0.0
Translation	(1.7)	2.7
Ending balance	422.3	417.2
Control Products & Solutions
Goodwill
Beginning balance	660.5	659.4
Acquisition of businesses	0.0	0.8
Divestiture of business (Note 13)		(10.3)
Translation	(7.3)	10.6
Ending balance	$ 653.2	$ 660.5

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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