v3.26.1
Cover Page - shares
3 Months Ended
Mar. 31, 2026
May 11, 2026
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2026  
Document Transition Report false  
Entity File Number 001-38693  
Entity Registrant Name Allogene Therapeutics, Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 82-3562771  
Entity Address, Address Line One 210 East Grand Avenue  
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 457-2700  
Title of 12(b) Security Common Stock, $0.001 par value per share  
Trading Symbol ALLO  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Emerging Growth Company false  
Entity Small Business true  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding (in shares)   345,154,561
Current Fiscal Year End Date --12-31  
Amendment Flag false  
Entity Central Index Key 0001737287  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q1