Receivables - Schedule of Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accounts Notes And Loans Receivable [Line Items]
Allowance at beginning of period	$ 13.0	$ 11.2	$ 11.3	$ 9.9
Provision for doubtful accounts, net of recoveries	(1.6)	0.4	0.7	1.8
Charge-off of accounts	(0.3)	(0.1)	(0.9)	(0.2)
Allowance at end of period	11.1	11.5	11.1	11.5
Finance
Accounts Notes And Loans Receivable [Line Items]
Allowance at beginning of period	3.1	2.4	2.2	2.8
Provision for doubtful accounts, net of recoveries	0.1	(0.1)	1.0	(0.5)
Allowance at end of period	3.2	2.3	3.2	2.3
Trade and Other
Accounts Notes And Loans Receivable [Line Items]
Allowance at beginning of period	9.9	8.8	8.7	7.1
Provision for doubtful accounts, net of recoveries	(1.7)	0.5	(0.3)	2.3
Charge-off of accounts	(0.3)	(0.1)	(0.5)	(0.2)
Allowance at end of period	$ 7.9	$ 9.2	7.9	$ 9.2
Notes
Accounts Notes And Loans Receivable [Line Items]
Allowance at beginning of period			0.4
Charge-off of accounts			$ (0.4)