Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 847	$ 823
Accumulated depreciation	(427)	(432)
Net property, plant and equipment	420	391
Non-cash accruals	13	39
Depreciation (includes capital leases)	49	42	$ 38
Land
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	51	51
Buildings
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	292	286
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	442	442
Construction in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	62	44
Assets Held under Capital Leases
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	22	28
Accumulated depreciation	$ (4)	$ (4)