Note 18 - California First National Bancorp (Parent Only) Financial Information - Condensed Balance Sheets (Details) (Parentheticals) - $ / shares	Jun. 30, 2017	Jun. 30, 2016
Preferred Stock, Shares Authorized	2,500,000	2,500,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized	20,000,000	20,000,000
Common stock, shares issued (in shares)	10,283,807	10,279,807
Common stock, shares outstanding (in shares)	10,283,807	10,279,807
Parent Company [Member]
Preferred Stock, Shares Authorized	2,500,000	2,500,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized	20,000,000	20,000,000
Common stock, shares issued (in shares)	10,283,807	10,279,807
Common stock, shares outstanding (in shares)	10,283,807	10,279,807