Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2022	Aug. 04, 2022
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Period End Date	Jun. 30, 2022
Document Transition Report	false
Entity File Number	000-29959
Entity Registrant Name	Cassava Sciences, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	91-1911336
Entity Address, Address Line One	7801 N. Capital of Texas Highway
Entity Address, Address Line Two	Suite 260
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
Title of 12(b) Security	Common Stock, $0.001 par value
Trading Symbol	SAVA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		40,097,917
Entity Central Index Key	0001069530