Note 1 - Summary of Significant Accounting Policies - Net Income Per Share Computation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator for net income per share – basic:
Net income	$ 30,971	$ 31,800	$ 37,466
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(8)	(16)	(18)
Net income attributable to common shareholders	$ 30,963	$ 31,784	$ 37,448
Denominator for net income per share – basic:
Weighted average common shares outstanding – basic (in shares)	24,540	24,922	25,422
Net income per share – basic (in dollars per share)	$ 1.26	$ 1.28	$ 1.47
Numerator for net income per share – diluted:
Net income attributable to common shareholders	$ 30,963	$ 31,784	$ 37,448
Weighted average common shares outstanding – basic (in shares)	24,540	24,922	25,422
Weighted average effect of dilutive securities – stock options (in shares)	133	130	218
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	24,673	25,052	25,640
Net income per share – diluted (in dollars per share)	$ 1.25	$ 1.27	$ 1.46