Note 2 - Summary of Significant Accounting Policies - Components of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash and cash equivalents	$ 6,937	$ 3,183
Restricted cash included in Other assets	475	475
Total cash, cash equivalents, and restricted cash in the statements of cash flows	$ 7,412	$ 3,658	$ 3,673	$ 9,986