Note 9 - Earnings Per Share - Net Income Per Share Computation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Net income	$ 9,657	$ 8,944	$ 9,232	$ 9,578	$ 7,715	$ 11,755	$ 27,833	$ 29,048
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(5)			(17)			(14)	(55)
Net income attributable to common shareholders	$ 9,652			$ 9,561			$ 27,819	$ 28,993
Weighted average common shares outstanding – basic (in shares)	25,427			25,219			25,423	25,113
Net income per share – basic (in dollars per share)	$ 0.38			$ 0.38			$ 1.09	$ 1.15
Net income attributable to common shareholders for basic computation	$ 9,652			$ 9,561			$ 27,819	$ 28,993
Weighted average effect of dilutive securities – stock options (in shares)	223			485			232	588
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	25,650			25,704			25,655	25,701
Net income per share - diluted (in dollars per share)	$ 0.38			$ 0.37			$ 1.08	$ 1.13