Intangible Assets - Indefinite-Lived Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
Indefinite-lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 0.6	$ 0.7
Gross Finite and Indefinite-Lived Intangible Assets	22.7		$ 22.7
Finite and Indefinited-Lived Accumulated Amortization and Impairment Charges	(11.0)		(10.4)
Intangible Assets, Net (Excluding Goodwill)	$ 11.7		$ 12.3