Note 4 - Fair Value Measurements - Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Total cash equivalents	$ 37,023	$ 6,114
Restricted cash	557	337
Total assets measured at fair value	37,580	6,451
Money Market Funds [Member]
Total cash equivalents	37,023	6,114
Fair Value, Inputs, Level 1 [Member]
Total cash equivalents	37,023	6,114
Restricted cash	557	337
Total assets measured at fair value	37,580	6,451
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Total cash equivalents	37,023	6,114
Fair Value, Inputs, Level 2 [Member]
Total cash equivalents	0	0
Restricted cash	0	0
Total assets measured at fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Total cash equivalents	$ 0	$ 0