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Taxes on Income - Narrative (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Examination [Line Items]
Effective income tax rate (as percent)	18.90%		17.80%		13.00%	28.40%
Research and development	$ 2,189		$ 2,274		$ 4,119	$ 5,470
Eisai
Income Tax Examination [Line Items]
Research and development				$ 1,400		$ 1,400
Internal Revenue Service (IRS) | Domestic Tax Authority
Income Tax Examination [Line Items]
Tax benefit recognized related to settlement					$ 360
Income taxes paid		$ 107

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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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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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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