Note 5 - Balance Sheet Components - Cash and Cash Equivalents and Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash and cash equivalents	$ 34,755	$ 44,013
Cash, cash equivalents and restricted cash	34,755	46,013	$ 143,745
Gross Unrealized Loss	(1)	(299)
Short-term investments	4,958	49,704
Investments and Cash	39,714	96,016
Investments and Cash, Fair Value Disclosure	39,713	95,717
Corporate securities	(1)	(299)
Corporate securities	4,958	49,704
US Treasury Securities [Member]
Amortized Cost	4,959	41,812
Gross Unrealized Loss	(1)	(270)
Estimated Fair Value	4,958	41,542
Short-term investments	4,958	41,542
Corporate securities	4,959	41,812
Corporate securities	(1)	(270)
Corporate securities	4,958	41,542
Corporate securities	4,958	41,542
Corporate Debt Securities [Member]
Amortized Cost		8,191
Gross Unrealized Loss		(29)
Estimated Fair Value		8,162
Short-term investments		8,162
Corporate securities		8,191
Corporate securities		(29)
Corporate securities		8,162
Corporate securities		8,162
Cash [Member]
Cash and cash equivalents	3,352	15,179
Money market funds, Fair Value	3,352	15,179
Cash, cash equivalents and restricted cash	3,352	15,179
Money Market Funds [Member]
Cash and cash equivalents	31,403	30,834
Money market funds, Fair Value	31,403	30,834
Cash, cash equivalents and restricted cash	$ 31,403	$ 30,834