| Document and Entity Information | Feb. 17, 2021 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Feb. 17, 2021 |
| Entity File Number | 001-37359 |
| Entity Registrant Name | Blueprint Medicines Corporation |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 26-3632015 |
| Entity Address, Address Line One | 45 Sidney Street |
| Entity Address, State or Province | MA |
| Entity Address, City or Town | Cambridge |
| Entity Address, Postal Zip Code | 02139 |
| City Area Code | 617 |
| Local Phone Number | 374-7580 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, par value $0.001 per share |
| Trading Symbol | BPMC |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001597264 |
| Amendment Flag | false |
