Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 314.2	$ 261.4	$ 759.5	$ 687.7
Other comprehensive income (loss), net of tax:
Pension and other postretirement benefit plan adjustments (net of tax (expense) of ($7.9), ($4.2), ($23.7), and ($12.8))	27.2	14.1	82.0	42.1
Currency translation adjustments	40.2	(2.7)	(12.0)	(12.2)
Net change in unrealized gains and losses on cash flow hedges (net of tax benefit of $5.0, $0.7, $3.5, and $6.7)	(11.4)	(1.9)	(9.4)	(20.2)
Net change in unrealized gains and losses on available-for-sale investments (net of tax (expense) of ($0.0), ($0.1), ($0.0), and ($0.4))	0.0	0.6	0.0	2.0
Other comprehensive income	56.0	10.1	60.6	11.7
Comprehensive income	370.2	271.5	820.1	699.4
Comprehensive loss attributable to noncontrolling interests	(3.5)	0.0	(1.7)	0.0
Comprehensive income attributable to Rockwell Automation, Inc.	$ 373.7	$ 271.5	$ 821.8	$ 699.4