Significant Accounting Policies - Calculation of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Oct. 31, 2020	Jul. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Basic and diluted net (loss) income per share computation
Net income (loss) attributable to common stockholders	$ 1	$ 75	$ 307	$ (641)	$ 76	$ (334)
Weighted Average common shares - basic (in shares)	13,064,191		11,619,686		12,811,921	11,619,569
Basic net income (loss) per share (in dollars per share)	$ 0		$ 0.03		$ 0.01	$ (0.03)
Net income (loss) available to common stockholders	$ 1		$ 307		$ 76	$ (334)
Incremental shares from assumed exercise of warrants and stock options (in shares)	1,997,912		1,345,106		1,751,139	0
Adjusted weighted average share - diluted (in shares)	15,062,103		12,964,792		14,563,060	11,619,569
Diluted net income (loss) per share (in usd per share)	$ 0		$ 0.02		$ 0.01	$ (0.03)