Document And Entity Information	3 Months Ended
	Dec. 31, 2012	Jan. 31, 2013
Document and Entity Information [Abstract]
Entity Registrant Name	DAILY JOURNAL CORP
Document Type	10-Q
Current Fiscal Year End Date	--09-30
Entity Common Stock, Shares Outstanding		1,380,746
Amendment Flag	true
Amendment Description	The purpose of this Amendment No. 1 to the Quarterly Report on Form 10-Q for Daily Journal Corporation (the “Company”) for the period ended December 31, 2012, filed with the Securities and Exchange Commission on February 14, 2013 (the “Form 10-Q”), is to correct unrealized gain figures in Note 8 under Part I, Item 1. The unrealized gain as of September 30, 2012 should be $52,464,000 (consisting of gross unrealized gains of $54,653,000 and gross unrealized losses of $2,189,000), as reflected in the table. The previous reported unrealized gain of $31,047,000 (consisting of gross unrealized gains of $34,742,000 and gross unrealized losses of $3,695,000) was at December 31, 2011. This Amendment No. 1 only affects Note 8 under Part I, Item 1 of the Form 10-Q and does not otherwise change or update the disclosures or financial information set forth in the Form 10-Q as originally filed and does not otherwise reflect events occurring after the original filing of the Form 10-Q.
Entity Central Index Key	0000783412
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Smaller Reporting Company
Entity Well-known Seasoned Issuer	No
Document Period End Date	Dec. 31, 2012
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q1