Note 5 - Amounts Reclassified Out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other-than-temporary impairment losses on investment securities	$ 0	$ (80)	$ 0	$ (80)
Income before income taxes	3,978	3,494	10,904	10,707
Tax effect	(767)	(940)	(1,896)	(2,907)
Net income	$ 3,211	2,554	9,008	7,800
Reclassification out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Unrealized net holding gains on available-for-sale securities		178	3	1,042
Other-than-temporary impairment losses on investment securities		(80)		(80)
Income before income taxes		98	3	962
Tax effect		(33)	(1)	(326)
Net income		$ 65	$ 2	$ 636