Note 5 - Amounts Reclassified Out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	$ 4,196	$ 3,492
Tax effect	(817)	(557)
Net income	3,379	2,935
Reclassification out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Unrealized net holding loss on available-for-sale securities	39	1
Income before income taxes	39	1
Tax effect	(8)
Net income	$ 31	$ 1