Note 5 - Stock-based Compensation (Details Textual) shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) shares	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) shares	Jun. 30, 2019 USD ($)
Number of Stock-based Compensation Plans in Effect	3		3
Share-based Payment Arrangement, Expense	$ 61,000	$ 55,000	$ 123,000	$ 80,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 292,000		$ 292,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares) | shares	0		0