v3.26.1
Cover - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2025
Mar. 23, 2026
Jun. 30, 2025
Document Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2025    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 001-38542    
Entity Registrant Name Kezar Life Sciences, Inc.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 47-3366145    
Entity Address, Address Line One 4000 Shoreline Court    
Entity Address, Address Line Two Suite 300    
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 822-5600    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 33
Entity Common Stock, Shares Outstanding   7,371,527  
Documents Incorporated by Reference
DOCUMENTS INCORPORATED BY REFERENCE
Portions of the definitive proxy statement for the 2026 Annual Meeting of Stockholders of the registrant, or the Proxy Statement, are incorporated by reference into Part III of this Annual Report on Form 10-K. The Proxy Statement or an Annual Report on Form 10-K/A will be filed with the Securities and Exchange Commission within 120 days of the registrant’s fiscal year ended December 31, 2025.
   
Entity Central Index Key 0001645666    
Document Fiscal Year Focus 2025    
Amendment Flag false    
Document Fiscal Period Focus FY    
Common Stock      
Document Information [Line Items]      
Title of 12(b) Security Common Stock, $0.001 par value    
Trading Symbol KZR    
Security Exchange Name NASDAQ    
Preferred Share Purchase Right      
Document Information [Line Items]      
Title of 12(b) Security Preferred Share Purchase Rights    
Security Exchange Name NASDAQ    
No Trading Symbol Flag true