Note 15 - Restricted Cash and Deposits (Details Textual) - USD ($)	Apr. 30, 2019	Apr. 30, 2018
Restricted Investments, Noncurrent	$ 469,000	$ 469,000
Cash Securing a Letter of Credit Issued as Security Deposit [Member]
Security Deposit	$ 469,000	$ 469,000

The amount of an asset, typically cash, provided to a counterparty to provide certain assurance of performance by the entity pursuant to the terms of a written or oral agreement, such as a lease.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.8,17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_SecurityDeposit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant