Note 2 - Summary of Significant Accounting Policies - Components of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash and cash equivalents	$ 5,708	$ 6,937
Restricted cash included in Other assets	475	475
Total cash, cash equivalents, and restricted cash in the statements of cash flows	$ 6,183	$ 7,412	$ 3,407	$ 3,658