Note 8 - Net Income Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net income used in the computation of basic and diluted net income per share (in thousands)	$ 3,921	$ 6,122	$ 9,078	$ 12,389
Weighted average shares outstanding - basic (in shares)	14,947,552	15,010,660	14,942,565	14,929,513
Dilutive common stock equivalents (in shares)	319,298	489,234	329,722	576,129
Weighted average number of shares outstanding during the period, diluted (in shares)	15,266,850	15,499,894	15,272,287	15,505,642
Basic (in dollars per share)	$ 0.26	$ 0.41	$ 0.61	$ 0.83
Diluted (in dollars per share)	$ 0.26	$ 0.39	$ 0.59	$ 0.80