Note 3 - Stock-based Compensation (Details Textual)	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) shares	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) shares	Jun. 30, 2016 USD ($)
Number of Stock-based Compensation Plans in Effect	3		3
Allocated Share-based Compensation Expense | $	$ 14,000	$ 5,000	$ 27,000	$ 10,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized | $	$ 105,000		$ 105,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	12,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	60,000		60,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period	12,000		12,000