Basis of Presentation and Accounting Policies - Reconciliation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Reconciled Basic and Diluted EPS
Net income attributable to Rockwell Automation	$ 1,358.1	$ 1,023.4	$ 695.8
Less: Allocation to participating securities	(2.1)	(1.0)	(0.7)
Net income available to common shareowners	$ 1,356.0	$ 1,022.4	$ 695.1
Basic weighted average outstanding shares (in shares)	116.0	115.8	118.3
Effect of dilutive securities
Diluted weighted average outstanding shares (in shares)	117.1	116.6	119.3
Earnings per share:
Basic (in dollars per share)	$ 11.69	$ 8.83	$ 5.88
Diluted (in dollars per share)	$ 11.58	$ 8.77	$ 5.83
Stock options
Effect of dilutive securities
Stock options (in shares)	1.0	0.7	0.9
Performance shares
Effect of dilutive securities
Stock options (in shares)	0.1	0.1	0.1