(Loss) Earnings Per Share - Calculations of (Loss) Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
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| Earnings Per Share [Abstract] | ||||
| Net (Loss) Income Attributable to Merck & Co., basic | $ (1,335) | $ 4,427 | $ (5,575) | $ 9,506 |
| Net (Loss) Income Attributable to Merck & Co., diluted | $ (1,335) | $ 4,427 | $ (5,575) | $ 9,506 |
| Average common shares outstanding (in shares) | 2,470 | 2,510 | 2,471 | 2,516 |
| Common shares issuable (in shares) | 0 | 3 | 0 | 6 |
| Average common shares outstanding assuming dilution (in shares) | 2,470 | 2,513 | 2,471 | 2,522 |
| Basic (Loss) Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share) | $ (0.54) | $ 1.76 | $ (2.26) | $ 3.78 |
| (Loss) Earnings per Common Share Assuming Dilution Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share) | $ (0.54) | $ 1.76 | $ (2.26) | $ 3.77 |
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- References No definition available.
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- Definition The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities, and addition from assumption of issuance of common shares for dilutive potential common shares; of income (loss) available to common shareholders. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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