Note 10 - Stock Compensation Plans (Details Textual) - USD ($)		1 Months Ended	4 Months Ended	12 Months Ended
		Aug. 31, 2000	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2015	Aug. 31, 2020	Jun. 30, 2015	Dec. 31, 2013
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total				$ 11,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)				0	0
The 2003 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)						3 years
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)						450,000
Sharebased Compensation Arrangement By Sharebased Payment Award Number Of Options Ungranted (in shares)									197,500
The 2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)								750,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)	[1],[2]			0	0
The Directors Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)		200,000
Sharebased Compensation Arrangement By Sharebased Payment Award Number Of Options Ungranted (in shares)		60,000
Number Of Options Each Director Received At Each Annual Meeting (in shares)		4,000
Options Vesting Percentage On First And Second Anniversary		50.00%
The Directors Plan [Member] | Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)		5,000
The 2011 Non-employee Director Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)							200,000
Three Independent Members of the Board of Directors [Member]
Share-Based Compensation Arrangement, Stock to be Granted Per Recipient, Value			$ 50,000
Share-based Payment Arrangement, Option [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)				2 years
Share-based Payment Arrangement, Option [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)				3 years

[1] Indicates plans with stock options.

[2] The 2015 Incentive Stock Plan (the "2015 Plan") was approved by shareholders in June 2015, which authorizes the issuance of up to 750,000 options to purchase shares of common stock to employees and key consultants and advisors.