Note 10 - Shareholders' Equity (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock Repurchased and Retired During Period, Shares	999,900	1,232,476
Payments for Repurchase of Common Stock	$ 3,580,000	$ 4,226,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 2,699,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	349,750	85,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	1,022,913	884,998	1,065,000
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	$ 356,000	$ 177,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Total	$ 648,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 295 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	211,835	111,669
Proceeds from Stock Options Exercised	$ 394,000	$ 210,000
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	145,000	130,000
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	4,639,750
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