| Cover | Aug. 08, 2024 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 08, 2024 |
| Entity File Number | 001-41905 |
| Entity Registrant Name | Cassava Sciences, Inc. |
| Entity Central Index Key | 0001069530 |
| Entity Tax Identification Number | 91-1911336 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 6801 N Capital of Texas Highway, Building 1; Suite 300 |
| Entity Address, City or Town | Austin |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 78731 |
| City Area Code | 512 |
| Local Phone Number | 501-2444 |
| 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 par value |
| Trading Symbol | SAVA |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
