Document And Entity Information (USD $)	12 Months Ended
	Jun. 30, 2012	Sep. 07, 2012	Dec. 31, 2011
Document and Entity Information [Abstract]
Entity Registrant Name	CALIFORNIA FIRST NATIONAL BANCORP
Document Type	10-K
Current Fiscal Year End Date	--06-30
Entity Common Stock, Shares Outstanding		10,447,227
Entity Public Float			$ 37,273,118
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	Jun. 30, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	FY