CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Statement [Abstract]
Sales	$ 15,035	$ 14,593	$ 29,522	$ 30,494
Costs, Expenses and Other
Cost of sales	4,024	4,216	7,951	9,596
Selling, general and administrative	2,702	2,512	5,182	4,834
Research and development	13,321	2,798	17,597	5,374
Restructuring costs	151	142	218	194
Other (income) expense, net	172	438	259	1,148
Total Costs, Expenses and Other	20,370	10,106	31,207	21,146
(Loss) Income Before Taxes	(5,335)	4,487	(1,685)	9,348
Income Tax Provision	637	538	1,462	1,092
Net (Loss) Income	(5,972)	3,949	(3,147)	8,256
Less: Net Income Attributable to Noncontrolling Interests	3	5	7	2
Net (Loss) Income Attributable to Merck & Co., Inc.	$ (5,975)	$ 3,944	$ (3,154)	$ 8,254
Basic (Loss) Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ (2.35)	$ 1.56	$ (1.24)	$ 3.26
(Loss) Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ (2.35)	$ 1.55	$ (1.24)	$ 3.25