Document And Entity Information	6 Months Ended
	Dec. 31, 2012	Feb. 08, 2013
Document and Entity Information [Abstract]
Entity Registrant Name	CALIFORNIA FIRST NATIONAL BANCORP
Document Type	10-Q
Current Fiscal Year End Date	--06-30
Entity Common Stock, Shares Outstanding		10,447,227
Amendment Flag	false
Entity Central Index Key	0000803016
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	Q2