Acquisition - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Business Acquisition [Line Items]
Purchase price paid in cash for acquisition	$ 13.2	$ 0.0	$ 0.0
Goodwill	182.6	$ 180.1	$ 167.0
Dynaloy, LLC
Business Acquisition [Line Items]
Purchase price paid in cash for acquisition	13.2
Goodwill	$ 5.0