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Taxes on Income - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Unrecognized tax benefits, reduction resulting from divestiture of Merck's consumer care business	$ (103)	$ (29)	$ (11)
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Balance January 1	1,893	1,723	3,494
Additions related to current year positions	199	221	146
Additions related to prior year positions	46	142	520
Reductions for tax positions of prior years	(454)	(73)	(1,038)
Settlements	(356)	(91)	(1,388)
Lapse of statute of limitations (2)	(103)	(29)	(11)
Balance December 31	1,225	$ 1,893	$ 1,723
consumer care business
Income Tax Contingency [Line Items]
Unrecognized tax benefits, reduction resulting from divestiture of Merck's consumer care business	(78)
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Lapse of statute of limitations (2)	$ (78)

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Amount of unrecognized tax benefits.

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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