Note 2 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Restricted Cash and Cash Equivalents, Total	$ 420
Restricted Cash and Cash Equivalents, Current, Total	150	$ 1,595	$ 2,771
Restricted Cash and Cash Equivalents, Noncurrent, Total	$ 270	$ 371	$ 362