Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Millions	Mar. 31, 2018	Sep. 30, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 381.6	$ 378.6
Less accumulated depreciation	(85.6)	(62.5)
Property, plant and equipment, net	296.0	316.1
Accumulated depreciation related to facilities and equipment acquired under capital leases	6.7	4.9
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	50.8	51.0
Plants and buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	107.3	106.5
Facilities and equipment acquired under capital leases	13.7	13.7
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	151.5	152.8
Facilities and equipment acquired under capital leases	27.4	27.2
Software and computer equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	64.8	63.3
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 7.2	$ 5.0