Intangible Assets - Components of Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 19,748	$ 19,530
Accumulated Amortization	5,981	4,555
Unamortized intangible assets	46	3
Acquired in-process research and development (a)
Finite And Indefinite Lived Intangible Assets [Line Items]
Unamortized intangible assets	44	1
Trademarks
Finite And Indefinite Lived Intangible Assets [Line Items]
Unamortized intangible assets	2	2
Developed technology
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	14,105	13,960
Accumulated Amortization	3,959	2,906
Customer relationships
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,616	4,608
Accumulated Amortization	1,509	1,183
Product rights
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	119	110
Accumulated Amortization	73	60
Trademarks
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	408	407
Accumulated Amortization	120	102
Patents and other
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	500	445
Accumulated Amortization	$ 320	$ 305