Note 18 - California First National Bancorp (Parent Only) Financial Information - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2014
Cash and cash equivalents	$ 96,055	$ 105,094	$ 60,240	$ 40,122
Other assets	1,306	2,108
Total assets	715,585	888,176	731,074
Accrued liabilities	2,536	3,622
Income taxes payable- deferred	5,569	12,674
Total liabilities	519,451	697,154
Preferred stock; 2,500,000 shares authorized; none issued
Common stock, $.01 par value; 20,000,000 shares authorized: 10,283,807 (2017) and 10,279,807 (2016) issued and outstanding	103	103
Additional paid in capital	2,309	2,240
Retained earnings	193,728	187,334
Other comprehensive income, net of tax	(6)	1,345
Total stockholders’ equity	196,134	191,022	188,218	183,745
Total liabilities and stockholders’ equity	715,585	888,176
Parent Company [Member]
Cash and cash equivalents	2,990	3,910	$ 3,091	$ 2,796
Intercompany receivable	22	3
Other assets	428	169
Premises and other fixed assets	54	124
Total assets	197,586	192,016
Accrued liabilities	381	470
Intercompany payable		123
Income taxes payable- deferred	1,071	401
Total liabilities	1,452	994
Preferred stock; 2,500,000 shares authorized; none issued
Common stock, $.01 par value; 20,000,000 shares authorized: 10,283,807 (2017) and 10,279,807 (2016) issued and outstanding	103	103
Additional paid in capital	2,309	2,240
Retained earnings	193,728	187,334
Other comprehensive income, net of tax	(6)	1,345
Total stockholders’ equity	196,134	191,022
Total liabilities and stockholders’ equity	197,586	192,016
Parent Company [Member] | Investments In Banking Subsidiary [Member]
Investment in subsidiary	126,483	117,573
Parent Company [Member] | Investments In Non-banking Subsidiary [Member]
Investment in subsidiary	$ 67,609	$ 70,237