| Cover Page | Jun. 11, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jun. 11, 2021 |
| Entity Registrant Name | ACCELERON PHARMA INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-36065 |
| Entity Tax Identification Number | 27-0072226 |
| Entity Address, Address Line One | 128 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 | 649-9200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.001 per share |
| Trading Symbol | XLRN |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001280600 |
| Amendment Flag | false |
