XML 110 R1.htm IDEA: XBRL DOCUMENT v3.20.1
Document and Entity Information - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Mar. 12, 2020
Jun. 28, 2019
Cover [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2019    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2019    
Entity Registrant Name AGENUS INC    
Entity Central Index Key 0001098972    
Trading Symbol AGEN    
Current Fiscal Year End Date --12-31    
Entity Filer Category Accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Current Reporting Status Yes    
Entity Well-known Seasoned Issuer No    
Entity Common Stock, Shares Outstanding   161,589,924  
Entity Public Float     $ 406.8
Entity Voluntary Filers No    
Entity Interactive Data Current Yes    
Title of 12(b) Security Common Stock, $.01 Par Value    
Security Exchange Name NASDAQ    
Entity File Number 000-29089    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 06-1562417    
Entity Address, Address Line One 3 Forbes Road    
Entity Address, City or Town Lexington    
Entity Address, State or Province MA    
Entity Address, Postal Zip Code 02421    
City Area Code 781    
Local Phone Number 674-4400    
Document Annual Report true    
Document Transition Report false    
Documents Incorporated by Reference [Text Block]

Portions of the Registrant’s Definitive Proxy Statement relating to the 2020 Annual Meeting of Stockholders, which the registrant intends to file with the Securities and Exchange Commission pursuant to Regulation 14A within 120 days after the end of the registrant’s fiscal year ended December 31, 2019, are incorporated by reference into Part III of this Report.