Note 5 - Employees' Profit Sharing and Savings Plan (Details Textual) - USD ($)	3 Months Ended
Jul. 31, 2016	Jul. 31, 2015
Deferred Compensation Arrangement with Individual, Employer Contribution	$ 108,000	$ 100,000

The amount of payment into the fund established for purposes of making future disbursements to the individual in accordance with the terms and understanding of the deferred compensation arrangement.

No definition available.

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