Intangible Assets, Goodwill, Acquisitions and Divestitures - Additional Information (Details) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($) Company	Sep. 30, 2021 USD ($) Company	Sep. 30, 2020 USD ($) Company Subsidiary	Sep. 30, 2019 USD ($)
Finite Lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 52.3	$ 55.8	$ 56.3
Weighted average amortization period for intangible assets		17 years
Goodwill impairment	$ 15.5	$ 0.0	$ 15.5
Number of unrelated maintenance services companies acquired | Company	6	8	6
Consideration paid, net of cash acquired		$ 110.4	$ 90.3	$ 64.0
Number of sale of fully owned subsidiaries | Subsidiary			2
Consideration amount on sale of business	$ 32.3		$ 32.3
Cash consideration received from divestiture			$ 29.3
Unrelated Maintenance Services Companies
Finite Lived Intangible Assets [Line Items]
Acquisition of operations, Percentage	100.00%	100.00%	100.00%
Selling, General and Administrative Expense
Finite Lived Intangible Assets [Line Items]
Pre-tax gain (loss) on sale of business			$ (5.7)
Promissory Note
Finite Lived Intangible Assets [Line Items]
Noncash or part noncash divestiture, amount of consideration received	$ 3.0		3.0
Customer Relationships and Non-compete Agreements
Finite Lived Intangible Assets [Line Items]
Identifiable assets acquired related to intangible assets	$ 26.7	$ 28.6	$ 26.7