XML 18 R1.htm IDEA: XBRL DOCUMENT v3.20.4
Document and Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2020
Feb. 25, 2021
Jun. 30, 2020
Cover [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2020    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY    
Trading Symbol CBIO    
Entity Registrant Name Catalyst Biosciences, Inc.    
Entity Central Index Key 0001124105    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Non-accelerated Filer    
Entity Shell Company false    
Entity Small Business true    
Entity Emerging Growth Company false    
Entity Common Stock, Shares Outstanding   31,331,027  
Entity Public Float     $ 128,362,589
ICFR Auditor Attestation Flag false    
Entity Interactive Data Current Yes    
Title of 12(b) Security Common stock    
Security Exchange Name NASDAQ    
Entity File Number 000-51173    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 56-2020050    
Entity Address, Address Line One 611 Gateway Blvd    
Entity Address, Address Line Two Suite 710    
Entity Address, City or Town South San Francisco    
Entity Address, State or Province CA    
Entity Address, Postal Zip Code 94080    
City Area Code 650    
Local Phone Number 871-0761    
Document Annual Report true    
Document Transition Report false