Note 10 - Shareholders' Equity (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock Repurchased and Retired During Period, Shares	683,910	999,900
Payments for Repurchase of Common Stock	$ 2,548,000	$ 3,580,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 2,152,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	370,000	349,750
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	1,326,414	1,022,913	884,998
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	0.00%	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 121,000	$ 356,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 589,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	1 year 332 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	66,499	211,835
Proceeds from Stock Options Exercised	$ 130,000
Share-based Payment Arrangement, Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	455,000	145,000
The2004 Plan Member
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	5,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	5,009,750
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	5 years