v3.25.1
Document And Entity Information - shares
 6 Months Ended
Mar. 31, 2025
Apr. 30, 2025
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2025  
Document Transition Report false  
Entity File Number 0-14665  
Entity Registrant Name DAILY JOURNAL CORPORATION  
Entity Incorporation, State or Country Code SC  
Entity Tax Identification Number 95-4133299  
Entity Address, Address Line One 915 East First Street  
Entity Address, Postal Zip Code 90012-4050  
Entity Address, City or Town Los Angeles  
Entity Address, State or Province CA  
City Area Code 213  
Local Phone Number 229-5300  
Title of 12(b) Security Common Stock  
Trading Symbol DJCO  
Security Exchange Name NASDAQ  
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  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding (in shares)   1,377,426
Entity Central Index Key 0000783412  
Current Fiscal Year End Date --09-30  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Amendment Flag false