Goodwill and Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	$ 117	$ 115
Accumulated Amortization	(20)	(19)
Net Intangible Assets, finite lives	97	96
Developed Technologies [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	51	50
Accumulated Amortization	(5)	(5)
Net Intangible Assets, finite lives	46	45
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	58	57
Accumulated Amortization	(15)	(14)
Net Intangible Assets, finite lives	$ 43	$ 43