Business Segment Information - Components of Identifiable Assets, Depreciation and Amortization, and Capital Expenditures for Property (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Identifiable assets	$ 6,262.0	$ 7,161.7	$ 7,101.2
Depreciation and amortization	164.6	168.9	172.2
Purchase accounting depreciation and amortization	17.4	21.4	18.4
Capital expenditures	125.5	141.7	116.9
Corporate
Segment Reporting Information [Line Items]
Identifiable assets	2,378.2	2,600.7	3,012.3
Depreciation and amortization	2.3	3.2	1.5
Capital expenditures	57.6	69.6	50.7
Operating Segments [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	147.2	147.5	153.8
Architecture & Software
Segment Reporting Information [Line Items]
Identifiable assets	1,788.9	2,482.8	2,054.3
Depreciation and amortization	72.5	69.3	75.0
Capital expenditures	29.4	30.0	24.7
Control Products & Solutions
Segment Reporting Information [Line Items]
Identifiable assets	2,094.9	2,078.2	2,034.6
Depreciation and amortization	72.4	75.0	77.3
Capital expenditures	$ 38.5	$ 42.1	$ 41.5