Intangible Assets - Components of Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 20,738	$ 7,811
Accumulated Amortization	2,112	1,986
Unamortized intangible assets	50	69
Acquired in-process research and development
Finite And Indefinite Lived Intangible Assets [Line Items]
Unamortized intangible assets	48	67
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	15,269	3,508
Accumulated Amortization	1,096	1,029
Customer relationships
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,559	3,393
Accumulated Amortization	621	564
Product rights
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	128	131
Accumulated Amortization	54	54
Trademarks
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	408	408
Accumulated Amortization	66	65
Patents and other
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	375	370
Accumulated Amortization	$ 274	$ 274