Segment Reporting - Profits to Income Before Taxes (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Profits	$ 3,428	$ 2,347	$ 10,784	$ 8,673
Interest income	9	61	48	225
Interest expense	(203)	(231)	(624)	(674)
Depreciation and amortization			(2,721)	(2,716)
Research and development	(3,390)	(3,204)	(7,721)	(7,324)
Restructuring costs	(114)	(232)	(269)	(444)
Total segment profits
Segment Reporting Information [Line Items]
Profits	8,424	8,168	23,347	22,678
Total segment profits \| Pharmaceutical segment
Segment Reporting Information [Line Items]
Profits	7,974	7,747	22,010	21,437
Total segment profits \| Animal Health segment
Segment Reporting Information [Line Items]
Profits	451	423	1,336	1,243
Total segment profits \| Other segment
Segment Reporting Information [Line Items]
Profits	(1)	(2)	1	(2)
Other profits
Segment Reporting Information [Line Items]
Profits	(12)	101	188	226
Unallocated
Segment Reporting Information [Line Items]
Interest income	9	61	48	225
Interest expense	(203)	(231)	(624)	(674)
Depreciation and amortization	(395)	(382)	(1,173)	(1,169)
Research and development	(3,272)	(3,110)	(7,364)	(7,045)
Amortization of purchase accounting adjustments	(285)	(329)	(879)	(1,105)
Restructuring costs	(114)	(232)	(269)	(444)
Other unallocated, net	$ (724)	$ (1,699)	$ (2,490)	$ (4,019)

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Other net expenses not allocated to segments.

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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