Note 9 - Net Income Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net income	$ 4,577	$ 15,174	$ 15,055	$ 18,541
Weighted average shares outstanding - basic (in shares)	15,433,412	15,016,062	15,327,374	15,020,457
Dilutive common stock equivalents (in shares)	654,324	155,024	712,231	165,535
Weighted average number of shares outstanding during the period, diluted (in shares)	16,087,736	15,171,086	16,039,605	15,185,992
Basic (in dollars per share)	$ 0.30	$ 1.01	$ 0.98	$ 1.23
Diluted (in dollars per share)	$ 0.28	$ 1.00	$ 0.94	$ 1.22