Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 315.4	$ 80.3
Net income	310.7	80.3
Other comprehensive income (loss), net of tax:
Pension and other postretirement benefit plan adjustments (net of tax (expense) of ($7.9) and ($4.3))	27.4	13.8
Currency translation adjustments	22.1	(28.5)
Net change in unrealized gains and losses on cash flow hedges (net of tax benefit of $1.1 and $6.5)	(2.5)	(20.8)
Net change in unrealized gains and losses on available-for-sale investments (net of tax (expense) of ($0.0) and ($0.1))	0.0	0.5
Other comprehensive income (loss)	47.0	(35.0)
Comprehensive income	362.4	45.3
Comprehensive income attributable to noncontrolling interests	5.0	0.0
Comprehensive income attributable to Rockwell Automation, Inc.	$ 357.4	$ 45.3