| Document and Entity Information | May 17, 2023 |
| Document And Entity Information [Line Items] | |
| Amendment Flag | false |
| Entity Central Index Key | 0000310158 |
| Document Type | 8-K |
| Document Period End Date | May 17, 2023 |
| Entity Registrant Name | Merck & Co., Inc. |
| Entity Incorporation State Country Code | NJ |
| Entity File Number | 1-6571 |
| Entity Tax Identification Number | 22-1918501 |
| Entity Address, Address Line One | 126 East Lincoln Avenue |
| Entity Address, City or Town | Rahway |
| Entity Address, State or Province | NJ |
| Entity Address, Postal Zip Code | 07065 |
| City Area Code | (908) |
| Local Phone Number | 740-4000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Common Stock ($0.50 par value) |
| Trading Symbol | MRK |
| Security Exchange Name | NYSE |
| A 0.500 Notesdue 2024 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 0.500% Notes due 2024 |
| Trading Symbol | MRK 24 |
| Security Exchange Name | NYSE |
| A 1.875 Notesdue 2026 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 1.875% Notes due 2026 |
| Trading Symbol | MRK/26 |
| Security Exchange Name | NYSE |
| A 2.500 Notesdue 2034 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 2.500% Notes due 2034 |
| Trading Symbol | MRK/34 |
| Security Exchange Name | NYSE |
| A 1.375 Notesdue 2036 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 1.375% Notes due 2036 |
| Trading Symbol | MRK 36A |
| Security Exchange Name | NYSE |
