Note 18 - California First National Bancorp (Parent Only) Financial Information - Condensed Statements of Earnings (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015
Salaries & benefits									$ 7,485	$ 7,254	$ 8,582
Occupancy									695	685	634
Professional services									1,060	1,117	971
Income (Loss) before taxes and equity in undistributed earnings of subsidiaries									18,724	14,068	14,815
Income tax expense									7,601	5,420	5,760
Net Income	$ 2,464	$ 2,511	$ 4,190	$ 1,958	$ 3,755	$ 1,611	$ 1,558	$ 1,724	11,123	8,648	9,055
Parent Company [Member]
Dividends from non-bank subsidiary									5,000	8,000	5,000
Other interest income									18	9	1
Total income									6,127	9,036	5,828
Salaries & benefits									1,625	1,508	1,209
Occupancy									156	146	95
Professional services									248	243	244
Other general & administrative									208	198	322
Total non-interest expenses									2,237	2,095	1,870
Income (Loss) before taxes and equity in undistributed earnings of subsidiaries									3,890	6,941	3,958
Income tax expense									400	(99)	(154)
Equity in undistributed earnings of subsidiaries									7,633	1,608	4,943
Net Income									11,123	8,648	9,055
Parent Company [Member] | Investments In Banking Subsidiary [Member]
Management fee income subsidiaries									968	968	676
Parent Company [Member] | Investments In Non-banking Subsidiary [Member]
Management fee income subsidiaries									$ 141	$ 59	$ 151