Goodwill and Other Intangible Assets - Changes in Carrying Amount of Goodwill (Details) $ in Millions	3 Months Ended
	Dec. 31, 2017 USD ($)
Goodwill
Balance at beginning of period	$ 1,077.7
Acquisition of business	6.8
Translation	(2.2)
Balance at end of period	1,082.3
Architecture & Software [Member]
Goodwill
Balance at beginning of period	417.2
Acquisition of business	6.8
Translation	(0.6)
Balance at end of period	423.4
Control Products & Solutions [Member]
Goodwill
Balance at beginning of period	660.5
Acquisition of business	0.0
Translation	(1.6)
Balance at end of period	$ 658.9