Note 9 - 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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net income	$ 8,196	$ 9,944	$ 23,251	$ 28,485
Weighted average shares outstanding - basic (in shares)	15,528,534	15,084,300	15,394,427	15,041,738
Dilutive common stock equivalents (in shares)	571,316	626,822	665,259	319,297
Weighted average number of shares outstanding during the period, diluted (in shares)	16,099,850	15,711,122	16,059,686	15,361,035
Basic (in dollars per share)	$ 0.53	$ 0.66	$ 1.51	$ 1.89
Diluted (in dollars per share)	$ 0.51	$ 0.63	$ 1.45	$ 1.85