Summary of Significant Accounting Policies - Intangibles (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Finite-Lived and Indefinite-Lived, Intangible Assets [Line Items]
Amortization of intangible assets	$ 51.2	$ 22.2	$ 22.2
Amortization of intangible assets, next twelve months	19.5
Amortization of intangible assets, year two	19.5
Amortization of intangible assets, year three	19.5
Amortization of intangible assets, year four	19.5
Amortization of intangible assets, year five	19.5
Accelerated amortization	29.9
Intangible Assets, Net
Finite-lived intangible assets, gross	376.8	425.9
Finite-Lived Intangible Assets, Accumulated Amortization	(153.7)	(151.6)
Finite-lived intangible assets, net	223.1	274.3
Customer relationships
Intangible Assets, Net
Finite-lived intangible assets, gross	178.6	209.4
Finite-Lived Intangible Assets, Accumulated Amortization	(75.3)	(76.9)
Finite-lived intangible assets, net	103.3	132.5
Trademarks
Intangible Assets, Net
Finite-lived intangible assets, gross	195.1	213.4
Finite-Lived Intangible Assets, Accumulated Amortization	(75.3)	(71.6)
Finite-lived intangible assets, net	119.8	141.8
Other intangible assets
Intangible Assets, Net
Finite-lived intangible assets, gross	3.1	3.1
Finite-Lived Intangible Assets, Accumulated Amortization	(3.1)	(3.1)
Finite-lived intangible assets, net	$ 0.0	$ 0.0