Receivables - Schedule of Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Accounts Notes And Loans Receivable [Line Items]
Allowance at beginning of period	$ 5.8	$ 9.7	$ 9.6	$ 11.3
Provision for doubtful accounts, net of recoveries	(0.1)	3.9	(3.9)	2.3
Charge-off of accounts		(0.6)		(0.6)
Allowance at end of period	5.7	13.0	5.7	13.0
Finance Receivables
Accounts Notes And Loans Receivable [Line Items]
Allowance at beginning of period	1.4	2.0	2.7	2.2
Provision for doubtful accounts, net of recoveries	(0.3)	1.1	(1.6)	0.9
Allowance at end of period	1.1	3.1	1.1	3.1
Notes Receivable
Accounts Notes And Loans Receivable [Line Items]
Allowance at beginning of period		0.4		0.4
Charge-off of accounts		(0.4)		(0.4)
Trade and Other Receivables
Accounts Notes And Loans Receivable [Line Items]
Allowance at beginning of period	4.4	7.3	6.9	8.7
Provision for doubtful accounts, net of recoveries	0.2	2.8	(2.3)	1.4
Charge-off of accounts		(0.2)		(0.2)
Allowance at end of period	$ 4.6	$ 9.9	$ 4.6	$ 9.9