Identifiable Intangible Assets - Summary of Identifiable Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount net of impairment	$ 20,292	$ 21,182
Accumulated amortization	12,460	12,259
Net carrying amount	7,832	8,923
Identifiable product rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount net of impairment	19,034	19,650
Accumulated amortization	12,234	12,094
Net carrying amount	6,800	7,556
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount net of impairment	635	621
Accumulated amortization	226	165
Net carrying amount	409	456
In Process Research and Development (IPR&D) [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount net of impairment	623	911
Accumulated amortization	0
Net carrying amount	$ 623	$ 911