Significant Accounting Policies - Calculation of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Oct. 31, 2021	Jul. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Oct. 31, 2021	Oct. 31, 2020
Basic and diluted net (loss) income per share computation
Net income attributable to common stockholders	$ 277	$ (172)	$ 1	$ 75	$ 105	$ 76
Weighted Average common shares - basic (in shares)	13,428,508		13,064,191		13,145,930	12,811,921
Basic net income per share (in dollars per share)	$ 0.02		$ 0		$ 0.01	$ 0.01
Net income available to common stockholders	$ 277		$ 1		$ 105	$ 76
Incremental shares from assumed exercise of warrants and stock options (in shares)	1,120,628		1,997,912		1,067,520	1,751,139
Adjusted weighted average share - diluted (in shares)	14,549,136		15,062,103		14,213,450	14,563,060
Diluted net income per share (in dollars per share)	$ 0.02		$ 0		$ 0.01	$ 0.01