Goodwill and Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Sep. 30, 2020
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	$ 135	$ 127
Accumulated Amortization	(28)	(24)
Net Intangible Assets, finite lives	107	103
Developed Technologies [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	63	60
Accumulated Amortization	(9)	(8)
Net Intangible Assets, finite lives	54	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	61	56
Accumulated Amortization	(18)	(15)
Net Intangible Assets, finite lives	$ 43	$ 41