Note 8 - Earnings Per Share - Net Income Per Share Computation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net income	$ 11,755	$ 8,196
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(23)	(28)
Net income attributable to common shareholders	$ 11,732	$ 8,168
Denominator for net income per share – basic:
Weighted average common shares outstanding – basic (in shares)	24,972	24,766
Net income per share – basic (in dollars per share)	$ 0.47	$ 0.33
Numerator for net income per share – diluted:
Net income attributable to common shareholders for basic computation	$ 11,732	$ 8,168
Weighted average common shares outstanding – basic (in shares)	24,972	24,766
Weighted average effect of dilutive securities – stock options (in shares)	753	743
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	25,725	25,509
Net income per share - diluted (in dollars per share)	$ 0.46	$ 0.32