Identifiable Intangible Assets - Summary of Identifiable Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount net of impairment	$ 21,998	$ 23,661
Accumulated amortization	10,766	9,656
Net carrying amount	11,232	14,005
Identifiable product rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount net of impairment	19,663	20,361
Accumulated amortization	10,640	9,565
Net carrying amount	9,023	10,796
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount net of impairment	600	606
Accumulated amortization	126	91
Net carrying amount	474	515
In Process Research and Development (IPR&D) [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount net of impairment	1,735	2,694
Net carrying amount	$ 1,735	$ 2,694