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
	Mar. 31, 2020	Mar. 31, 2019
Net income	$ 5,342,000	$ 1,218,000
Shares (denominator):
Basic weighted average common shares outstanding (in shares)	13,121,867	13,391,992
Add: dilutive effect of common stock options (in shares)	542,843	77,505
Diluted weighted average common shares outstanding (in shares)	13,664,710	13,469,497
Earnings per common share:
Basic (in dollars per share)	$ 0.41	$ 0.09
Diluted (in dollars per share)	$ 0.39	$ 0.09