Note 11 - Defined Contribution Plan (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0	$ 0

Amount of discretionary contributions made by an employer to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration