Intangible Assets, Goodwill, Acquisitions and Divestitures - Schedule of Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 672.8	$ 647.1
Accumulated Amortization	(451.5)	(395.6)
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	666.3	639.6
Accumulated Amortization	$ (448.3)	(393.3)
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	4.8
Accumulated Amortization	$ (2.0)	(1.7)
Trademarks | Minimum
Finite Lived Intangible Assets [Line Items]
Useful Life	4 years
Trademarks | Maximum
Finite Lived Intangible Assets [Line Items]
Useful Life	12 years
Noncompete Agreements
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 2.7	2.7
Accumulated Amortization	$ (1.2)	$ (0.6)
Noncompete Agreements | Minimum
Finite Lived Intangible Assets [Line Items]
Useful Life	5 years