Note 3 - Summary of Significant Accounting Policies - Computation of Basic Net Income Per Share (Details) - shares		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Weighted average common shares outstanding, basic (in shares)	[1]	1,008,979	1,029,001
Common shares upon exercise of options (in shares)	[1]	12,886	10,598
Weighted average common shares outstanding, diluted (in shares)	[1]	1,021,865	1,039,599

[1] Common shares of 40,402 and 39,402 underlying outstanding stock options for the years ended December 31, 2019 and 2018, respectively, were excluded from the computation of diluted earnings per share as their inclusion would be antidilutive.