Business Segment Information - Components of Identifiable Assets, Depreciation and Amortization, and Capital Expenditures for Property (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Identifiable assets	$ 6,113.0	$ 6,262.0	$ 7,161.7
Depreciation and amortization	152.2	164.6	168.9
Purchase accounting depreciation and amortization	16.6	17.4	21.4
Capital expenditures	132.8	125.5	141.7
Corporate
Segment Reporting Information [Line Items]
Identifiable assets	2,587.7	2,378.2	2,600.7
Depreciation and amortization	2.2	2.3	3.2
Capital expenditures	6.2	57.6	69.6
Total
Segment Reporting Information [Line Items]
Depreciation and amortization	135.6	147.2	147.5
Architecture & Software
Segment Reporting Information [Line Items]
Identifiable assets	1,410.5	1,788.9	2,482.8
Depreciation and amortization	63.8	72.5	69.3
Capital expenditures	57.7	29.4	30.0
Control Products & Solutions
Segment Reporting Information [Line Items]
Identifiable assets	2,114.8	2,094.9	2,078.2
Depreciation and amortization	69.6	72.4	75.0
Capital expenditures	$ 68.9	$ 38.5	$ 42.1