Intangible Assets - Acquired Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	$ 133.0	$ 130.0
Accumulated Amortization	(62.2)	(55.2)
Net	70.8	74.8
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	79.5	80.4
Accumulated Amortization	(22.7)	(19.5)
Net	56.8	60.9
Patents and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	50.3	46.4
Accumulated Amortization	(37.9)	(34.2)
Net	12.4	12.2
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	3.2	3.2
Accumulated Amortization	(1.6)	(1.5)
Net	$ 1.6	$ 1.7