Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Millions	Jun. 30, 2017	Sep. 30, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 370.1	$ 336.2
Less accumulated depreciation	(48.7)	(13.6)
Property, plant and equipment, net	321.4	322.6
Accumulated depreciation related to facilities and equipment acquired under capital leases	3.3	1.1
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	50.8	50.4
Plants and buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	105.3	89.8
Facilities and equipment acquired under capital leases	13.7
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	148.1	130.5
Facilities and equipment acquired under capital leases	25.6	25.2
Software and computer equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	59.5	49.0
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 6.4	$ 16.5