Note 13 - 401(k) Benefit Plan (Details Textual) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	1.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0.2	$ 0.2

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