Note 8 - 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, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Net income	$ 9,578	$ 7,715	$ 11,755	$ 8,119	$ 7,393	$ 8,196	$ 29,048	$ 23,708
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(17)			(27)			(55)	(80)
Net income attributable to common shareholders	$ 9,561			$ 8,092			$ 28,993	$ 23,628
Weighted average common shares outstanding – basic (in shares)	25,219			24,827			25,113	24,794
Net income per share – basic (in dollars per share)	$ 0.38			$ 0.33			$ 1.15	$ 0.95
Net income attributable to common shareholders for basic computation	$ 9,561			$ 8,092			$ 28,993	$ 23,628
Weighted average effect of dilutive securities – stock options (in shares)	485			914			588	830
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	25,704			25,741			25,701	25,624
Net income per share - diluted (in dollars per share)	$ 0.37			$ 0.31			$ 1.13	$ 0.92