Note 2 - Summary of Significant Accounting Policies - Reconciliation of Net Income and Number of Shares Used in Computations of Basic and Diluted EPS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Net income	$ 6,756,000	$ 26,888,000
Shares (denominator):
Basic weighted average common shares outstanding (in shares)	13,225,628	13,449,987
Add: Dilutive effect of common stock options (in shares)	273,814	522,158
Diluted weighted average common shares outstanding (in shares)	13,499,442	13,972,145
Earnings per common share:
Basic earnings per common share (in dollars per share)	$ 0.51	$ 2.00
Diluted earnings per common share (in dollars per share)	$ 0.50	$ 1.92