Business Segment Information - Sales and Operating Results (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Sales and operating results of reportable segments
Sales	$ 1,776.1	$ 1,681.3	$ 3,341.4	$ 3,365.8
Purchase accounting depreciation and amortization	(13.1)	(9.5)	(24.8)	(19.5)
Corporate and other	(30.4)	(17.7)	(58.4)	(50.5)
Non-operating pension and postretirement benefit cost	(7.0)	(8.6)	(14.0)	(17.3)
Gain (loss) on investments	190.9	(144.8)	581.3	(73.8)
Legal Settlement	0.0	0.0	70.0	0.0
Interest (expense) income - net	(22.8)	(23.5)	(45.1)	(47.5)
Income before income taxes	507.7	167.4	1,208.4	502.0
Operating Segments
Sales and operating results of reportable segments
Sales	1,776.1	1,681.3	3,341.4	3,365.8
Segment operating earnings	390.1	371.5	699.4	710.6
Intelligent Devices
Sales and operating results of reportable segments
Sales	850.2	785.0	1,571.9	1,561.7
Intelligent Devices | Operating Segments
Sales and operating results of reportable segments
Sales	850.2	785.0	1,571.9	1,561.6
Segment operating earnings	202.0	180.7	342.2	341.3
Software & Control
Sales and operating results of reportable segments
Sales	502.3	448.2	943.3	900.7
Software & Control | Operating Segments
Sales and operating results of reportable segments
Sales	502.3	448.2	943.3	900.7
Segment operating earnings	149.8	136.8	282.9	277.2
Lifecycle Services
Sales and operating results of reportable segments
Sales	423.6	448.1	826.2	903.4
Lifecycle Services | Operating Segments
Sales and operating results of reportable segments
Sales	423.6	448.1	826.2	903.5
Segment operating earnings	$ 38.3	$ 54.0	$ 74.3	$ 92.1