Intangible Assets, net (Details) - USD ($) $ in Millions	Mar. 31, 2020	Sep. 30, 2019
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	$ 425.9	$ 425.9
Finite-lived intangible assets, accumulated amortization	(140.5)	(129.4)
Finite-lived intangible assets, net	285.4	296.5
Customer relationships
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	209.4	209.4
Finite-lived intangible assets, accumulated amortization	(71.2)	(65.5)
Finite-lived intangible assets, net	138.2	143.9
Trademarks
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	213.4	213.4
Finite-lived intangible assets, accumulated amortization	(66.2)	(60.8)
Finite-lived intangible assets, net	147.2	152.6
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