Intangible Assets, Goodwill and Acquisitions - Schedule of Intangible Assets (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2022	Sep. 30, 2021
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 728.8	$ 701.4
Accumulated Amortization	(542.4)	503.8
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	722.3	694.9
Accumulated Amortization	$ (537.8)	(499.8)
Customer Relationships | Minimum
Finite Lived Intangible Assets [Line Items]
Useful Life	6 years
Customer Relationships | Maximum
Finite Lived Intangible Assets [Line Items]
Useful Life	21 years
Trademarks
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3.8	3.8
Accumulated Amortization	$ (2.5)	(2.3)
Trademarks | Maximum
Finite Lived Intangible Assets [Line Items]
Useful Life	12 years
Noncompete Agreements
Finite Lived Intangible Assets [Line Items]
Useful Life	5 years
Gross Carrying Amount	$ 2.7	2.7
Accumulated Amortization	$ (2.1)	$ (1.7)