v3.25.3
Cover
Oct. 16, 2025
Document Information [Line Items]  
Document Type 8-K
Document Period End Date Oct. 16, 2025
Entity Registrant Name Kezar Life Sciences, Inc.
Entity Incorporation, State or Country Code DE
Entity File Number 001-38542
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
Written Communications false
Soliciting Material false
Pre-commencement Tender Offer false
Pre-commencement Issuer Tender Offer false
Entity Emerging Growth Company false
Amendment Flag false
Entity Central Index Key 0001645666
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 Rights  
Document Information [Line Items]  
Title of 12(b) Security Preferred Share Purchase Rights
Security Exchange Name NASDAQ
No Trading Symbol Flag true