Note 18 - California First National Bancorp (Parent Only) Financial Information - Condensed Statements of Cash Flows (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
Net income	$ 2,464	$ 2,511	$ 4,190	$ 1,958	$ 3,755	$ 1,611	$ 1,558	$ 1,724	$ 11,123	$ 8,648	$ 9,055
Deferred income taxes									(4,829)	(5,621)	(3,959)
Other, net									390	(320)	37
Net cash provided by (used) for operating activities									44,328	9,685	5,169
Net cash provided by (used for) investing activities									115,811	(117,109)	(131,896)
Payments to repurchase common stock										(2,360)
Dividends to stockholders									(4,729)	(4,603)	(4,393)
Net cash used for financing activities									(169,178)	152,278	146,845
NET CHANGE IN CASH AND CASH EQUIVALENTS									(9,039)	44,854	20,118
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD				105,094				60,240	105,094	60,240	40,122
CASH AND CASH EQUIVALENTS AT END OF PERIOD	96,055				105,094				96,055	105,094	60,240
Parent Company [Member]
Net income									11,123	8,648	9,055
Deferred income taxes									670	122	49
Equity in undistributed earnings of subsidiaries									(7,633)	(1,608)	(4,943)
Net change in other liabilities									(89)	(22)	(3)
Net change in other assets									(254)	500	510
Other, net									70	73	64
Net cash provided by (used) for operating activities									3,887	7,713	4,732
Payments for investments in and (advances to) subsidiaries									(142)	69	(44)
Net cash provided by (used for) investing activities									(142)	69	(44)
Proceeds from issuance of common stock									64
Payments to repurchase common stock										(2,360)
Dividends to stockholders									(4,729)	(4,603)	(4,393)
Net cash used for financing activities									(4,665)	(6,963)	(4,393)
NET CHANGE IN CASH AND CASH EQUIVALENTS									(920)	819	295
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD				$ 3,910				$ 3,091	3,910	3,091	2,796
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 2,990				$ 3,910				$ 2,990	$ 3,910	$ 3,091