Supplemental Balance Sheet Information - Summary of Accounts Receivable (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Current
Trade	$ 64.0	$ 56.2
Other	17.9	14.3
Notes receivable from franchisees	0.0	0.2
Receivables, gross	81.9	70.7
Allowance for credit losses	(0.6)	(4.6)
Receivables, net	81.3	66.1
Non-current
Notes receivable	2.3	2.1
Other	7.5	0.1
Noncurrent notes receivable, gross	9.8	2.2
Allowance for losses	(2.4)	(2.2)
Noncurrent notes receivable, net	$ 7.4	$ 0.0