CONDENSED CONSOLIDATED STATEMENT OF INCOME - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Income Statement [Abstract]
Sales	$ 15,806	$ 16,112	$ 31,335	$ 31,887
Costs, Expenses and Other
Cost of sales	3,557	3,745	6,976	7,285
Selling, general and administrative	2,649	2,739	5,202	5,221
Research and development	4,048	3,500	7,669	7,492
Restructuring costs	560	80	629	202
Other (income) expense, net	(7)	42	(43)	12
Total Costs, Expenses and Other	10,807	10,106	20,433	20,212
Income Before Taxes	4,999	6,006	10,902	11,675
Taxes on Income	571	545	1,388	1,447
Net Income	4,428	5,461	9,514	10,228
Less: Net Income Attributable to Noncontrolling Interests	1	6	8	11
Net Income Attributable to Merck & Co., Inc.	$ 4,427	$ 5,455	$ 9,506	$ 10,217
Basic Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 1.76	$ 2.15	$ 3.78	$ 4.03
Earnings per Common Share Assuming Dilution Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 1.76	$ 2.14	$ 3.77	$ 4.02

Total of cost of sales, operating expenses and nonoperating income or expense.

No definition available.

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Namespace Prefix:	mrk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.