Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Quarterly Financial Information (Unaudited)
Sales	$ 1,570.0	$ 1,394.0	$ 1,681.3	$ 1,684.5	$ 1,730.2	$ 1,665.1	$ 1,657.2	$ 1,642.3	$ 6,329.8	$ 6,694.8	$ 6,666.0
Gross profit	639.3	554.2	698.8	702.9	722.9	730.3	708.2	738.7	2,595.2	2,900.1	2,884.9
Income before income taxes	299.6	334.5	167.4	334.6	56.4	321.4	402.4	120.8	1,136.1	901.0	1,330.8
Net income attributable to Rockwell Automation, Inc.	$ 262.7	$ 317.8	$ 132.2	$ 310.7	$ 8.1	$ 261.4	$ 346.0	$ 80.3	$ 1,023.4	$ 695.8	$ 535.5
Earnings per share:
Basic (in dollars per share)	$ 2.26	$ 2.74	$ 1.14	$ 2.68	$ 0.07	$ 2.22	$ 2.91	$ 0.67	$ 8.83	$ 5.88	$ 4.27
Diluted (in dollars per share)	$ 2.25	$ 2.73	$ 1.13	$ 2.66	$ 0.07	$ 2.20	$ 2.88	$ 0.66	$ 8.77	$ 5.83	$ 4.21