Consolidated Statement of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Statement of Comprehensive Income [Abstract]
Net Income Attributable to Merck & Co., Inc.	$ 17,117	$ 365	$ 14,519
Other Comprehensive Income (Loss) Net of Taxes:
Net unrealized income (loss) on derivatives, net of reclassifications	266	(97)	(71)
Benefit plan net gain (loss) and prior service credit (cost), net of amortization	466	(385)	335
Cumulative translation adjustment	(516)	89	(603)
Other comprehensive income (loss), net of taxes	216	(393)	(339)
Comprehensive Income (Loss) Attributable to Merck & Co., Inc.	$ 17,333	$ (28)	$ 14,180