Intangible Assets - Components of Intangible Assets (Detail) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 19,537	$ 19,475
Accumulated Amortization	4,198	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	13,972	13,966
Accumulated Amortization	2,638	1,782
Customer relationships
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,610	4,584
Accumulated Amortization	1,102	861
Product rights
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	115	121
Accumulated Amortization	60	58
Trademarks
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	407	407
Accumulated Amortization	97	84
Patents and other
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	433	397
Accumulated Amortization	$ 301	$ 288