Goodwill and Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Sep. 30, 2020
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	$ 132	$ 127
Accumulated Amortization	(29)	(24)
Net Intangible Assets, finite lives	103	103
Developed Technologies [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	62	60
Accumulated Amortization	(10)	(8)
Net Intangible Assets, finite lives	52	52
Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	11	11
Accumulated Amortization	(1)	(1)
Net Intangible Assets, finite lives	10	10
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	59	56
Accumulated Amortization	(18)	(15)
Net Intangible Assets, finite lives	$ 41	$ 41