Note 9 - Basic and Diluted Earnings Per Common Share - Reconciliation of Net Income and Number of Shares Used in Computations of Basic and Diluted EPS (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net income	$ 6,220,000	$ 1,010,000	$ 11,561,000	$ 2,228,000
Shares (denominator):
Basic weighted average common shares outstanding (in shares)	13,351,675	13,184,321	13,351,674	13,287,583
Add: dilutive effect of common stock options (in shares)	300,320	23,817	461,420	58,563
Diluted weighted average common shares outstanding (in shares)	13,651,995	13,208,138	13,813,094	13,346,146
Earnings per common share:
Basic (in dollars per share)	$ 0.47	$ 0.08	$ 0.87	$ 0.17
Diluted (in dollars per share)	$ 0.46	$ 0.08	$ 0.84	$ 0.17