Intangible Assets - Gross and Net Intangible Assets by Major Class (Details) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	$ 11.7
Computer Software, Intangible Asset [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Computer Software, Gross	2.7	$ 2.7
Finite-Lived Intangible Assets, Accumulated Amortization	(2.5)	(2.5)
Finite-Lived Intangible Assets, Net	0.2	0.2
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Customer Lists, Gross	20.0	20.0
Finite-Lived Intangible Assets, Accumulated Amortization	(8.5)	(7.9)
Finite-Lived Intangible Assets, Net	$ 11.5	$ 12.1