| Cover | Aug. 09, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Aug. 9, 2021 |
| Entity Registrant Name | ATHERSYS, INC / NEW |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-33876 |
| Entity Tax Identification Number | 20-4864095 |
| Entity Address, Address Line One | 3201 Carnegie Avenue, |
| Entity Address, City or Town | Cleveland, |
| Entity Address, State or Province | OH |
| Entity Address, Postal Zip Code | 44115-2634 |
| City Area Code | 216 |
| Local Phone Number | 431-9900 |
| 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 | ATHX |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001368148 |
