| Cover | Sep. 16, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Sep. 16, 2020 |
| Entity File Number | 001-35403 |
| Entity Registrant Name | Verastem, Inc. |
| Entity Central Index Key | 0001526119 |
| Entity Tax Identification Number | 27-3269467 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 117 Kendrick Street |
| Entity Address, Address Line Two | Suite 500 |
| Entity Address, City or Town | Needham |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02494 |
| City Area Code | 781 |
| Local Phone Number | 292-4200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, $0.0001 par value per share |
| Trading Symbol | VSTM |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
