Note 4 - Fair Value Measurements - Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Total cash equivalents		$ 37,023
Restricted cash		557
Total assets measured at fair value		37,580
Money Market Funds [Member]
Total cash equivalents		37,023
Fair Value, Inputs, Level 1 [Member]
Total cash equivalents	$ 32,161	37,023
Restricted cash	221	557
Total assets measured at fair value	32,382	37,580
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Total cash equivalents	32,161	$ 37,023
Fair Value, Inputs, Level 2 [Member]
Total cash equivalents	32,161
Restricted cash	221
Total assets measured at fair value	32,382
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Total cash equivalents	$ 32,161