Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 269.0	$ 314.2	$ 1,269.7	$ 759.5
Other comprehensive income (loss), net of tax:
Pension and other postretirement benefit plan adjustments (net of tax (expense) of ($142.9), ($7.9), ($159.6) and ($23.7))	426.5	27.2	482.1	82.0
Currency translation adjustments	23.0	40.2	58.9	(12.0)
Net change in unrealized gains and losses on cash flow hedges (net of tax (expense) benefit of ($0.4), $5.0, $0.6 and $3.5	0.8	(11.4)	(2.4)	(9.4)
Other comprehensive income	450.3	56.0	538.6	60.6
Comprehensive income	719.3	370.2	1,808.3	820.1
Comprehensive loss attributable to noncontrolling interests	(3.0)	(3.5)	(10.5)	(1.7)
Comprehensive income attributable to Rockwell Automation, Inc.	$ 722.3	$ 373.7	$ 1,818.8	$ 821.8