Earnings Per Share - Summary of Potentially Dilutive Stock-based Instruments (Details) - shares	12 Months Ended
Apr. 30, 2019	Apr. 30, 2018
Class of Stock [Line Items]
Total common stock equivalents	4,095,066	4,710,129
Stock options
Class of Stock [Line Items]
Total common stock equivalents	2,423,626	2,705,845
Warrants
Class of Stock [Line Items]
Total common stock equivalents	1,671,440	2,004,284

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration