Goodwill and Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Sep. 30, 2018
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	$ 108	$ 111
Accumulated Amortization	(14)	(13)
Net Intangible Assets, finite lives	94	98
Developed Technologies [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	51	52
Accumulated Amortization	(2)	(2)
Net Intangible Assets, finite lives	49	50
Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	8	8
Net Intangible Assets, finite lives	8	8
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	49	51
Accumulated Amortization	(12)	(11)
Net Intangible Assets, finite lives	$ 37	$ 40