Intangible Assets - Indefinite-Lived Intangible Assets (Details) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017
Indefinite-lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 1.1	$ 1.4
Gross Finite and Indefinite-Lived Intangible Assets	22.7		$ 22.7
Finite and Indefinited-Lived Accumulated Amortization and Impairment Charges	(11.5)		(10.4)
Intangible Assets, Net (Excluding Goodwill)	$ 11.2		$ 12.3