Financial Instruments - Schedule of Income Statement Effects on Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Currency Swap \| Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Pretax Loss (Gain) Recognized in Income	$ 36	$ (20)
Foreign Exchange Future \| Sales
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Pretax Loss (Gain) Recognized in Income	$ 12	$ 16

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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+ Details

Merck & Co., Inc. 10-Q