Note 3 - Cash and Investments - Cash, Cash Equivalents and Short-term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash	$ 6,509				$ 4,092
Cash equivalents (see detail in Note 4)	6,114				3,620
Restricted cash	337				600
Total cash, cash equivalents and restricted cash as presented in the statement of cash flows	12,960				8,312				$ 10,531
Short-term investments (see detail in Note 4)					2,249
Total cash, cash equivalents, restricted cash and short-term investments	$ 12,960	$ 12,572	$ 12,582	$ 10,644	$ 10,561	$ 11,610	$ 12,560	$ 15,000