Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Millions	Mar. 31, 2022	Sep. 30, 2021
Other intangible assets
Amortized intangible assets, carrying amount	$ 1,197.0	$ 1,188.0
Amortized intangible assets, accumulated amortization	272.2	209.9
Amortized intangible assets, net	924.8	978.1
Total, carrying amount	1,240.7	1,231.7
Total, net	968.5	1,021.8
Goodwill and Other Intangible Assets (Textual) [Abstract]
Estimated amortization expense in 2022	112.5
Estimated amortization expense in 2023	111.3
Estimated amortization expense in 2024	108.3
Estimated amortization expense in 2025	105.9
Estimated amortization expense in 2026	104.2
Trademarks
Other intangible assets
Allen-Bradley trademark not subject to amortization	43.7	43.7
Software products
Other intangible assets
Amortized intangible assets, carrying amount	96.4	90.4
Amortized intangible assets, accumulated amortization	53.2	43.2
Amortized intangible assets, net	43.2	47.2
Customer relationships
Other intangible assets
Amortized intangible assets, carrying amount	596.7	595.9
Amortized intangible assets, accumulated amortization	95.6	75.4
Amortized intangible assets, net	501.1	520.5
Technology
Other intangible assets
Amortized intangible assets, carrying amount	421.6	420.8
Amortized intangible assets, accumulated amortization	98.2	71.7
Amortized intangible assets, net	323.4	349.1
Trademarks
Other intangible assets
Amortized intangible assets, carrying amount	75.2	73.8
Amortized intangible assets, accumulated amortization	18.9	13.3
Amortized intangible assets, net	56.3	60.5
Other
Other intangible assets
Amortized intangible assets, carrying amount	7.1	7.1
Amortized intangible assets, accumulated amortization	6.3	6.3
Amortized intangible assets, net	$ 0.8	$ 0.8