Intangible Assets - Components of Intangible Assets (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Sep. 30, 2019
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 19,697	$ 19,530
Accumulated Amortization	5,634	4,555
Unamortized intangible assets	46	3
Trademarks
Finite And Indefinite Lived Intangible Assets [Line Items]
Unamortized intangible assets	2	2
Acquired in-process research and development (a)
Finite And Indefinite Lived Intangible Assets [Line Items]
Unamortized intangible assets	44	1
Developed technology
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	14,059	13,960
Accumulated Amortization	3,702	2,906
Customer relationships
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,612	4,608
Accumulated Amortization	1,427	1,183
Product rights
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	115	110
Accumulated Amortization	68	60
Trademarks
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	408	407
Accumulated Amortization	115	102
Patents and other
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	503	445
Accumulated Amortization	$ 322	$ 305