Income Taxes - Components of Net Deferred Tax Asset and Liability Accounts (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Deferred tax assets:
Interest rate swaps	$ 1.4	$ 3.3
Self-insurance reserves	29.6	27.4
Deferred compensation	2.7	2.7
Payroll related accruals	18.3	15.8
Other accrued expenses	1.8	5.1
Allowance for doubtful accounts	0.8	0.8
Lease liabilities	17.7	16.6
Net operating loss carryforward	11.2	5.5
Other non-current deferred tax assets	1.8	2.3
Total non-current deferred tax assets	85.3	79.5
Total deferred tax assets	85.3	79.5
Deferred tax liabilities:
Intangible assets	49.0	53.2
Property and equipment	79.0	42.3
Deferred revenue	8.7	7.1
Prepaid assets	0.4	0.5
Lease assets	15.9	14.8
Other non-current deferred tax liabilities	0.5	0.5
Total non-current deferred tax liabilities	153.5	118.4
Total deferred tax liabilities	68.2	38.9
Classification on balance sheets:
Other Assets	2.6
Deferred Tax Liabilities	$ 70.8	$ 38.9