Intangible Assets, net (Details) - USD ($) $ in Millions	Jun. 30, 2020	Sep. 30, 2019
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	$ 425.9	$ 425.9
Finite-lived intangible assets, accumulated amortization	(146.0)	(129.4)
Finite-lived intangible assets, net	279.9	296.5
Customer relationships
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	209.3	209.4
Finite-lived intangible assets, accumulated amortization	(74.0)	(65.5)
Finite-lived intangible assets, net	135.3	143.9
Trademarks
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	213.5	213.4
Finite-lived intangible assets, accumulated amortization	(68.9)	(60.8)
Finite-lived intangible assets, net	144.6	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