Note 18 - Quarterly Financial Information (Unaudited) - Condensed Balance Sheet (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, cash equivalents, restricted cash and short-term investments	$ 12,960	$ 12,572	$ 12,582	$ 10,644	$ 10,561	$ 11,610	$ 12,560	$ 15,000
Total current assets	20,002	19,062	20,245	22,002	20,515	21,442	22,897	26,428
Total assets	22,282	21,063	22,075	23,973	23,055	23,056	24,967	29,673
Total current liabilities	11,339	10,544	11,422	12,856	11,200	11,226	11,882	12,464
Total shareholders' equity	$ 8,651	$ 8,622	$ 8,432	$ 9,401	$ 9,696	$ 10,888	$ 11,835	$ 15,673	$ 18,341