Goodwill and Other Intangible Assets (Details 1) - USD ($) $ in Millions	Jun. 30, 2017	Sep. 30, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Total, carrying amount	$ 483.6	$ 485.0
Total, net	231.9	255.3
Other intangible assets
Amortized intangible assets, carrying amount	439.9	441.3
Amortized intangible assets, accumulated amortization	251.7	229.7
Amortized intangible assets, net	188.2	211.6
Goodwill and Other Intangible Assets (Textual) [Abstract]
Estimated amortization expense in 2017	29.9
Estimated amortization expense in 2018	25.1
Estimated amortization expense in 2019	21.9
Estimated amortization expense in 2020	19.1
Estimated amortization expense in 2021	18.4
Trademarks [Member]
Indefinite-lived Intangible Assets [Line Items]
Allen-Bradley® trademark not subject to amortization	43.7	43.7
Computer software products [Member]
Other intangible assets
Amortized intangible assets, carrying amount	182.7	182.4
Amortized intangible assets, accumulated amortization	110.6	103.4
Amortized intangible assets, net	72.1	79.0
Customer relationships [Member]
Other intangible assets
Amortized intangible assets, carrying amount	112.0	112.6
Amortized intangible assets, accumulated amortization	57.7	51.9
Amortized intangible assets, net	54.3	60.7
Technology [Member]
Other intangible assets
Amortized intangible assets, carrying amount	103.4	103.9
Amortized intangible assets, accumulated amortization	54.9	48.5
Amortized intangible assets, net	48.5	55.4
Trademarks [Member]
Other intangible assets
Amortized intangible assets, carrying amount	31.0	31.4
Amortized intangible assets, accumulated amortization	19.3	17.0
Amortized intangible assets, net	11.7	14.4
Other [Member]
Other intangible assets
Amortized intangible assets, carrying amount	10.8	11.0
Amortized intangible assets, accumulated amortization	9.2	8.9
Amortized intangible assets, net	$ 1.6	$ 2.1