Goodwill and Other Intangible Assets - Changes in Carrying Amount of Goodwill (Details) $ in Millions	9 Months Ended
	Jun. 30, 2018 USD ($)
Goodwill
Balance at beginning of period	$ 1,077.7
Acquisition of business	6.8
Translation	(6.0)
Balance at end of period	1,078.5
Architecture & Software [Member]
Goodwill
Balance at beginning of period	417.2
Acquisition of business	6.8
Translation	(1.0)
Balance at end of period	423.0
Control Products & Solutions [Member]
Goodwill
Balance at beginning of period	660.5
Acquisition of business	0.0
Translation	(5.0)
Balance at end of period	$ 655.5