Note 3 - Summary of Significant Accounting Policies - Summary of Assets and Liabilities Measured at Fair Value on a Recurring and Nonrecurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Warrant liabilities	$ 1,505	$ 107
Fair Value, Inputs, Level 1 [Member]
Warrant liabilities
Fair Value, Inputs, Level 2 [Member]
Warrant liabilities
Fair Value, Inputs, Level 3 [Member]
Warrant liabilities	$ 1,505	$ 107