Intangible Assets, Goodwill, Acquisitions and Divestitures - Additional Information (Details) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($) Company	Sep. 30, 2020 USD ($) Company Subsidiary	Sep. 30, 2019 USD ($) Company	Sep. 30, 2018 USD ($)
Finite Lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 55.8	$ 56.3	$ 104.9
Weighted average amortization period for intangible assets		17 years 6 months
Goodwill impairment	$ 15.5	$ 15.5
Acquisition of operations, Percentage	100.00%	100.00%	100.00%
Number of unrelated maintenance services companies acquired | Company	6	6	6
Consideration paid, net of cash acquired		$ 90.3	$ 64.0	$ 104.4
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
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	$ 26.7	$ 17.2