Note 5 - Employees' Profit Sharing and Savings Plan (Details Textual) - USD ($)	9 Months Ended
Jan. 31, 2018	Jan. 31, 2017
Deferred Compensation Arrangement with Individual, Contributions by Employer	$ 345,000	$ 321,000

Amount of contributions made by employer into fund established for purposes of making future disbursement to individual in accordance with deferred compensation arrangement.

No definition available.

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