| Document and Entity Information | Jan. 25, 2024 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jan. 25, 2024 |
| Entity Registrant Name | Repare Therapeutics Inc. |
| Entity Incorporation State Country Code | A8 |
| Entity File Number | 001-39335 |
| Entity Tax Identification Number | 00-0000000 |
| Entity Address Address Line 1 | 7171 Frederick-Banting, Building 2, |
| Entity Address, Address Line Two | Suite 270 |
| Entity Address City Or Town | St-Laurent |
| Entity Address State Or Province | QC |
| Entity Address Country | CA |
| Entity Address Postal Zip Code | H4S 1Z9 |
| City Area Code | 857 |
| Local Phone Number | 412-7018 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common shares, no par value |
| Trading Symbol | RPTX |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001808158 |
