Intangible Assets, net (Details) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	$ 376.8	$ 376.8
Finite-lived intangible assets, accumulated amortization	(158.6)	(153.7)
Finite-lived intangible assets, net	218.2	223.1
Customer relationships
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	178.6	178.6
Finite-lived intangible assets, accumulated amortization	(77.8)	(75.3)
Finite-lived intangible assets, net	100.8	103.3
Trademarks and brands
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	195.1	195.1
Finite-lived intangible assets, accumulated amortization	(77.7)	(75.3)
Finite-lived intangible assets, net	117.4	119.8
Other intangible assets
Finite-Lived Intangible Assets
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