Segment Reporting - Reconciliation of Segment Profits to Income Before Taxes (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Profits	$ 3,259	$ 2,086	$ 6,326	$ 3,432
Interest income	75	81	164	165
Interest expense	(233)	(194)	(442)	(379)
Depreciation and amortization			(1,871)	(2,427)
Research and development	(2,189)	(2,274)	(4,119)	(5,470)
Restructuring costs	(59)	(228)	(212)	(323)
Total segment profits
Segment Reporting Information [Line Items]
Profits	7,518	6,451	14,510	12,866
Total segment profits \| Pharmaceutical segment
Segment Reporting Information [Line Items]
Profits	7,115	5,975	13,690	11,914
Total segment profits \| Animal Health segment
Segment Reporting Information [Line Items]
Profits	405	450	820	864
Total segment profits \| Other segments
Segment Reporting Information [Line Items]
Profits	(2)	26	0	88
Other profits (losses)
Segment Reporting Information [Line Items]
Profits	94	(2)	124	(89)
Unallocated
Segment Reporting Information [Line Items]
Interest income	75	81	164	165
Interest expense	(233)	(194)	(442)	(379)
Depreciation and amortization	(427)	(332)	(786)	(682)
Research and development	(2,093)	(2,190)	(3,935)	(5,307)
Amortization of purchase accounting adjustments	(378)	(732)	(775)	(1,464)
Restructuring costs	(59)	(228)	(212)	(323)
Other unallocated, net	$ (1,238)	$ (768)	$ (2,322)	$ (1,355)

Amortization of purchase accounting adjustments.

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Other net expenses not allocated to segments.

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The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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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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Amount of the cost of borrowed funds accounted for as interest expense.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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