Note 2 - Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash and cash equivalents at beginning of year	$ 3,979	$ 12,646	$ 4,617
Restricted cash at beginning of year	523
Cash, cash equivalents and restricted cash at beginning of year	4,502	12,646	4,617
Cash and cash equivalents at end of year	23,351	3,979	12,646
Restricted cash at end of year		523
CASH, CASH EQUIVALENTS AND RESTRICTED CASH AT END OF YEAR	$ 23,351	$ 4,502	$ 12,646