Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Goodwill
Beginning balance	$ 1,073.9	$ 1,028.8
Acquisition of businesses	0.8	72.7
Divestiture of business (Note 13)	(10.3)
Translation	13.3	(27.6)
Ending balance	1,077.7	1,073.9
Architecture and Software [Member]
Goodwill
Beginning balance	414.5	388.0
Acquisition of businesses	0.0	35.0
Divestiture of business (Note 13)	0.0
Translation	2.7	(8.5)
Ending balance	417.2	414.5
Control Products and Solutions [Member]
Goodwill
Beginning balance	659.4	640.8
Acquisition of businesses	0.8	37.7
Divestiture of business (Note 13)	(10.3)
Translation	10.6	(19.1)
Ending balance	$ 660.5	$ 659.4