Note 5 - Stockholders' Equity (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Apr. 30, 2020	Apr. 30, 2019
Stock Issued During Period, Shares, Employee Benefit Plan (in shares)	1,711,555	2,311,268
Stock Issued During Period, Shares, Employee Benefit Plan	$ 676	$ 584

Value of shares issued during the period to an employee benefit plan, such as a defined contribution or defined benefit plan.

No definition available.

Name:	us-gaap_StockIssuedDuringPeriodValueEmployeeBenefitPlan
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration