Note 14 - Employee Benefit Plan (Details Textual) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	140.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	5.00%
Defined Contribution Plan, Employer Matching Contribution, Amount	$ 0.8	$ 0.6	$ 0.6

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

No definition available.

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