Note 3 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Restricted cash held as a certificate of deposit	$ 324	$ 332
Deposit held as a certificate of deposit	152	152
Total assets	476	484
Fair Value, Inputs, Level 1 [Member]
Restricted cash held as a certificate of deposit	324	332
Deposit held as a certificate of deposit	152	152
Total assets	476	$ 484
Fair Value, Inputs, Level 2 [Member]
Restricted cash held as a certificate of deposit	0
Deposit held as a certificate of deposit	0
Total assets	0
Fair Value, Inputs, Level 3 [Member]
Restricted cash held as a certificate of deposit	0
Deposit held as a certificate of deposit	0
Total assets	$ 0