Provision for Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2013
Income Tax Disclosure [Abstract]
Valuation allowance	$ 15,300	$ 15,300
Operating loss carryforwards	46,900	$ 45,000
Operating loss, limitations on use	$ 432		$ 12,000

The portion of the valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from net operating loss carryforwards for which it is more likely than not that a tax benefit will not be realized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32537-109319

Name:	us-gaap_OperatingLossCarryforwardsValuationAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant