Note 9 - Earnings Per Share - Net Income Per Share Computation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Net income	$ 8,944	$ 9,232	$ 7,715	$ 11,755	$ 18,176	$ 19,470
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(5)		(15)		(10)	(38)
Net income attributable to common shareholders	$ 8,939		$ 7,700		$ 18,166	$ 19,432
Weighted average common shares outstanding – basic (in shares)	25,426		25,148		25,420	25,060
Net income per share – basic (in dollars per share)	$ 0.35		$ 0.31		$ 0.71	$ 0.78
Net income attributable to common shareholders for basic computation	$ 8,939		$ 7,700		$ 18,166	$ 19,432
Weighted average effect of dilutive securities – stock options (in shares)	219		532		236	642
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	25,645		25,680		25,656	25,702
Net income per share - diluted (in dollars per share)	$ 0.35		$ 0.30		$ 0.71	$ 0.76