Document And Entity Information - shares	3 Months Ended
	Dec. 31, 2022	Jan. 31, 2023
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Dec. 31, 2022
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, City or Town	Los Angeles
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	90012-4050
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)		1,377,026
Entity Central Index Key	0000783412
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Amendment Flag	false