Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 129.9	$ 346.0	$ 445.3	$ 426.3
Other comprehensive income (loss), net of tax:
Pension and other postretirement benefit plan adjustments (net of tax (expense) of ($8.0), ($4.3), ($15.8), and ($8.6))	27.4	14.2	54.8	28.0
Currency translation adjustments	(74.3)	19.0	(52.2)	(9.5)
Net change in unrealized gains and losses on cash flow hedges (net of tax (expense) benefit of ($2.6), ($0.5), ($1.5), and $6.0)	4.5	2.5	2.0	(18.3)
Net change in unrealized gains and losses on available-for-sale investments (net of tax (expense) of ($0.0), ($0.2), ($0.0), and ($0.3))	0.0	0.9	0.0	1.4
Other comprehensive (loss) income	(42.4)	36.6	4.6	1.6
Comprehensive income	87.5	382.6	449.9	427.9
Comprehensive (loss) income attributable to noncontrolling interests	(3.2)	0.0	1.8	0.0
Comprehensive income attributable to Rockwell Automation, Inc.	$ 90.7	$ 382.6	$ 448.1	$ 427.9