Related Party Transactions - Narrative (Details) - Board of Directors - USD ($) $ in Thousands	12 Months Ended
Apr. 30, 2021	Apr. 30, 2020
Board Member One
Related Party Transaction [Line Items]
Related related party transaction, amounts of transaction	$ 54	$ 72
Board Member Two
Related Party Transaction [Line Items]
Related related party transaction, amounts of transaction	$ 17	$ 48

Amount of transactions with related party during the financial reporting period.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864

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