Intangible Assets - Components of Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 19,530	$ 19,475
Accumulated Amortization	4,555	3,073
Unamortized intangible assets	3	39
Acquired in-process research and development (a)
Finite And Indefinite Lived Intangible Assets [Line Items]
Unamortized intangible assets	1	37
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	13,960	13,966
Accumulated Amortization	2,906	1,782
Customer relationships
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,608	4,584
Accumulated Amortization	1,183	861
Product rights
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	110	121
Accumulated Amortization	60	58
Trademarks
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	407	407
Accumulated Amortization	102	84
Patents and other
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	445	397
Accumulated Amortization	$ 305	$ 288