Significant Accounting Policies - Summary of Potentially Antidilutive Securities (Details) - shares	3 Months Ended
	Jul. 31, 2020	Jul. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents (in shares)	2,276,263	4,044,648
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents (in shares)	2,276,263	2,374,875
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents (in shares)	0	1,669,773