Segment, Geographic and Other Revenue Information - Footnotes (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Segment Reporting Information [Line Items]
Intangible asset impairment charge				$ 900
Gain on completion of Consumer Healthcare JV transaction		$ 0	$ 8,087	6	$ 8,087
IPR&D [Member]
Segment Reporting Information [Line Items]
Intangible asset impairment charge	[1]			900
Operating Segments [Member] | IPR&D [Member] | Biopharma [Member]
Segment Reporting Information [Line Items]
Intangible asset impairment charge		900		900
ViiV [Member]
Segment Reporting Information [Line Items]
Dividend income		$ 44	43	$ 196	$ 184
GSK Consumer Healthcare [Member]
Segment Reporting Information [Line Items]
Gain on completion of Consumer Healthcare JV transaction			$ 8,100

[1] Reflects intangible assets written down to fair value in the first nine months of 2020. Fair value was determined using the income approach, specifically the multi-period excess earnings method, also known as the discounted cash flow method. We started with a forecast of all the expected net cash flows associated with the asset and then applied an asset-specific discount rate to arrive at a net present value amount. Some of the more significant estimates and assumptions inherent in this approach include: the amount and timing of the projected net cash flows, which includes the expected impact of competitive, legal and/or regulatory forces on the product; the discount rate, which seeks to reflect the various risks inherent in the projected cash flows; and the tax rate, which seeks to incorporate the geographic diversity of the projected cash flows.