Note 12 - Retirement Plan (Details Textual) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 1.4	$ 1.1	$ 0.8
Maximum [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	50.00%

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration