| Document and Entity Information | Mar. 31, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001439222 |
| Document Type | 8-K |
| Document Period End Date | Mar. 31, 2021 |
| Entity Registrant Name | Agios Pharmaceuticals, Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-36014 |
| Entity Tax Identification Number | 26-0662915 |
| Entity Address, Address Line One | 88 Sidney Street |
| Entity Address, City or Town | Cambridge |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02139 |
| City Area Code | (617) |
| Local Phone Number | 649-8600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, Par Value $0.001 per share |
| Trading Symbol | AGIO |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
