Intangible Assets - Acquired Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	$ 133.0	$ 133.0
Accumulated Amortization	(69.5)	(62.2)
Net	63.5	70.8
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	79.5	79.5
Accumulated Amortization	(26.5)	(22.7)
Net	53.0	56.8
Patents and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	50.3	50.3
Accumulated Amortization	(41.3)	(37.9)
Net	9.0	12.4
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	3.2	3.2
Accumulated Amortization	(1.7)	(1.6)
Net	$ 1.5	$ 1.6