Note 9 - Net Income Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Net income	$ 10,478	$ 3,367
Weighted average shares outstanding - basic (in shares)	15,221,336	15,024,851
Dilutive common stock equivalents (in shares)	770,138	176,047
Weighted average number of shares outstanding during the period, diluted (in shares)	15,991,474	15,200,898
Basic (in dollars per share)	$ 0.69	$ 0.22
Diluted (in dollars per share)	$ 0.66	$ 0.22