Note 1 - Significant Accounting Policies and Related Matters - Computation of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net income	$ 8,465	$ 7,502	$ 8,098	$ 6,040	$ 5,627	$ 5,456	$ 3,515	$ 6,038	$ 30,105	$ 20,636	$ 26,907
Weighted-average shares outstanding: (in shares)									22,217	21,975	21,157
Earnings per share of common stock: (in dollars per share)	$ 0.38	$ 0.34	$ 0.36	$ 0.27	$ 0.26	$ 0.25	$ 0.16	$ 0.28	$ 1.36	$ 0.94	$ 1.27
Common stock equivalents, if dilutive (in shares)									206	196	318
Diluted (in shares)									22,423	22,171	21,475
Diluted (in dollars per share)	$ 0.38	$ 0.33	$ 0.36	$ 0.27	$ 0.25	$ 0.25	$ 0.16	$ 0.27	$ 1.34	$ 0.93	$ 1.25
Shares excluded in computing diluted earnings per share as those shares would be anti-dilutive (in shares)									295	293	10