Note 9 - Earnings Per Share - Net Income Per Share Computation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Net income	$ 9,232	$ 11,755
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(6)	(23)
Net income attributable to common shareholders	$ 9,226	$ 11,732
Weighted average common shares outstanding – basic (in shares)	25,414	24,972
Net income per share – basic (in dollars per share)	$ 0.36	$ 0.47
Net income attributable to common shareholders for basic computation	$ 9,226	$ 11,732
Weighted average effect of dilutive securities – stock options (in shares)	254	753
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	25,668	25,725
Net income per share - diluted (in dollars per share)	$ 0.36	$ 0.46