Note 4 - Stock-based Compensation (Details Textual)	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($)
Number of Stock-based Compensation Plans in Effect	3		3
Allocated Share-based Compensation Expense | $	$ 12,000	$ 7,000	$ 39,000	$ 17,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized | $	$ 90,000		$ 90,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	5,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period	6,000		18,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			60,000