Note 10 - Shareholders' Equity (Details Textual) - USD ($) xbrli-pure in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock Repurchased and Retired During Period, Shares	1,232,476	2,453,900
Payments for Repurchase of Common Stock	$ 4,226,000	$ 6,773,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 2,279,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	85,000	855,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	884,998	1,065,000	225,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 177,000	$ 29,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 528,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 197 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	111,669	15,000
Proceeds from Stock Options Exercised	$ 210,000	$ 17,000
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	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	4,290,000
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