Acquisitions, Divestitures, Equity-Method Investments, Licensing Arrangements and Collaborative Arrangements - Equity Method Investment (Details) - USD ($)		3 Months Ended		7 Months Ended	12 Months Ended
	Jul. 31, 2019	Dec. 31, 2019	Sep. 29, 2019	Jul. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Gain on completion of transaction					$ 6,000,000	$ 8,086,000,000	$ 0
Equity-method investments		$ 17,133,000,000			16,856,000,000	$ 17,133,000,000
Consumer Healthcare JV [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	32.00%	32.00%		32.00%		32.00%
Gain on completion of transaction			$ 8,100,000,000
Gain on completion of transaction, after-tax			$ 5,400,000,000
Equity-method investments		$ 17,000,000,000.0			16,700,000,000	$ 17,000,000,000.0
Dividend received					932,000,000
Equity method investment earnings		47,000,000			417,000,000
Increase due to foreign currency translation					$ 345,000,000
Equity method investments	$ 15,700,000,000	15,700,000,000		$ 15,700,000,000		15,700,000,000
Underlying equity in net assets	11,200,000,000	11,000,000,000.0		11,200,000,000		11,000,000,000.0
Difference between carrying amount and underlying equity	$ 4,500,000,000	4,800,000,000		$ 4,500,000,000		4,800,000,000
Administrative services, term	24 months
Manufacture and supply, term	6 years
ViiV [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage					11.70%
Equity-method investments								$ 0
Dividend income					$ 278,000,000	$ 220,000,000	253,000,000
GSK [Member] | Consumer Healthcare JV [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	68.00%			68.00%
Other Nonoperating Income (Expense) [Member] | Consumer Healthcare JV [Member]
Schedule of Equity Method Investments [Line Items]
Excess basis amortization and write-off		$ 31,000,000			$ 119,000,000
Consumer Healthcare [Member] | Held-for-sale, Not Discontinued Operations [Member]
Schedule of Equity Method Investments [Line Items]
Pre-tax income attributable to disposal group				$ 654,000,000			$ 977,000,000
Minimum [Member] | Consumer Healthcare JV [Member]
Schedule of Equity Method Investments [Line Items]
Excess basis amortization period					8 years
Maximum [Member] | Consumer Healthcare JV [Member]
Schedule of Equity Method Investments [Line Items]
Excess basis amortization period					20 years