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Note 10 - Stockholders' Equity (Details Textual) - USD ($)			12 Months Ended
	Dec. 09, 2016	Nov. 30, 2006	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 12, 2007
Common Stock, Par or Stated Value Per Share (in dollars per share)			$ 0.01	$ 0.01
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)			618,500	417,000
Share-based Payment Arrangement, Expense			$ 316,000	$ 243,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)			333,500
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in shares)			0	0
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total			$ 730,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			3 years 5 months 26 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value			$ 160,000	$ 113,000
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)			4 years
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)			10 years
Restricted Stock Units (RSUs) [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total			$ 3,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			2 months 12 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value			$ 38,000	$ 91,000
Share-based Payment Arrangement, Tranche Three [Member] \| Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage			25.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)	7 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)	10 years
The 2001 Non-qualified Stock Option Plan [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)		300,000
Common Stock, Par or Stated Value Per Share (in dollars per share)		$ 0.01
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)		4 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)			0	7,000	22,930
The 2007 Share Incentive Plan [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)						750,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)			220,000	345,000	345,000
The 2016 Share Incentive Plan [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)	750,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)			398,500	65,000	65,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)			333,500