Goodwill and Other Intangible Assets (Details 1) - USD ($) $ in Millions	Dec. 31, 2016	Sep. 30, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Total, carrying amount	$ 479.0	$ 485.0
Total, net	246.2	255.3
Other intangible assets
Amortized intangible assets, carrying amount	435.3	441.3
Amortized intangible assets, accumulated amortization	232.8	229.7
Amortized intangible assets, net	202.5	211.6
Goodwill and Other Intangible Assets (Textual) [Abstract]
Estimated amortization expense in 2017	29.6
Estimated amortization expense in 2018	24.9
Estimated amortization expense in 2019	21.7
Estimated amortization expense in 2020	19.0
Estimated amortization expense in 2021	18.3
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	182.4	182.4
Amortized intangible assets, accumulated amortization	105.9	103.4
Amortized intangible assets, net	76.5	79.0
Customer relationships [Member]
Other intangible assets
Amortized intangible assets, carrying amount	109.6	112.6
Amortized intangible assets, accumulated amortization	51.7	51.9
Amortized intangible assets, net	57.9	60.7
Technology [Member]
Other intangible assets
Amortized intangible assets, carrying amount	102.7	103.9
Amortized intangible assets, accumulated amortization	49.7	48.5
Amortized intangible assets, net	53.0	55.4
Trademarks [Member]
Other intangible assets
Amortized intangible assets, carrying amount	30.3	31.4
Amortized intangible assets, accumulated amortization	17.0	17.0
Amortized intangible assets, net	13.3	14.4
Other [Member]
Other intangible assets
Amortized intangible assets, carrying amount	10.3	11.0
Amortized intangible assets, accumulated amortization	8.5	8.9
Amortized intangible assets, net	$ 1.8	$ 2.1