Note 2 - Summary of Significant Accounting Policies - Financial Assets Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Inputs, Level 1 [Member] | Warrant Liability [Member]
Fair value of warrant liability	$ 0	$ 0
Fair Value, Inputs, Level 2 [Member] | Warrant Liability [Member]
Fair value of warrant liability	0	0
Fair Value, Inputs, Level 3 [Member] | Warrant Liability [Member]
Fair value of warrant liability	1,063	3,473
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents, fair value	27,955	43,574
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents, fair value	0	0
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents, fair value	0	0
Restricted Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents, fair value	2,546	3,055
Restricted Cash [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents, fair value	0	0
Restricted Cash [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents, fair value	$ 0	$ 0