Goodwill and Other Intangible Assets (Details 1) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Finite-Lived Intangible Assets [Line Items]
Intangible assets acquired during year		$ 57.5
Other intangible assets
Amortized intangible assets, carrying amount	$ 457.8	441.3
Amortized intangible assets, accumulated amortization	263.5	229.7
Amortized intangible assets, net	194.3	211.6
Intangible asset amortization expense	30.2	28.9	$ 29.4
Allen-Bradley® trademark not subject to amortization	43.7	43.7
Total other intangible assets, carrying amount	501.5	485.0
Total other intangible assets, net	238.0	255.3
Goodwill and Other Intangible Assets (Textuals) [Abstract]
Estimated amortization expense in 2018	27.5
Estimated amortization expense in 2019	24.5
Estimated amortization expense in 2020	21.4
Estimated amortization expense in 2021	20.6
Estimated amortization expense in 2022	18.7
Computer software products [Member]
Other intangible assets
Amortized intangible assets, carrying amount	194.8	182.4
Amortized intangible assets, accumulated amortization	113.2	103.4
Amortized intangible assets, net	81.6	79.0
Intangible asset amortization expense	9.8	11.5	$ 9.4
Customer relationships [Member]
Other intangible assets
Amortized intangible assets, carrying amount	114.5	112.6
Amortized intangible assets, accumulated amortization	61.5	51.9
Amortized intangible assets, net	53.0	60.7
Technology [Member]
Other intangible assets
Amortized intangible assets, carrying amount	104.8	103.9
Amortized intangible assets, accumulated amortization	57.9	48.5
Amortized intangible assets, net	46.9	55.4
Trademarks [Member]
Other intangible assets
Amortized intangible assets, carrying amount	32.3	31.4
Amortized intangible assets, accumulated amortization	21.1	17.0
Amortized intangible assets, net	11.2	14.4
Other [Member]
Other intangible assets
Amortized intangible assets, carrying amount	11.4	11.0
Amortized intangible assets, accumulated amortization	9.8	8.9
Amortized intangible assets, net	$ 1.6	$ 2.1