Significant Accounting Policies - Calculation of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Jan. 31, 2021	Jan. 31, 2020
Basic and diluted net (loss) income per share computation
Net income attributable to common stockholders	$ 740	$ 1	$ 75	$ 407	$ 307	$ (641)	$ 816	$ 72
Weighted Average common shares - basic (in shares)	13,371,613			11,752,619			12,974,470	11,653,115
Basic net income per share (in dollars per share)	$ 0.06			$ 0.03			$ 0.06	$ 0.01
Net income available to common stockholders	$ 740			$ 407			$ 816	$ 72
Incremental shares from assumed exercise of warrants and stock options (in shares)	1,135,542			1,921,053			1,535,810	1,787,746
Adjusted weighted average share - diluted (in shares)	14,507,155			13,673,672			14,510,280	13,440,861
Diluted net income per share (in dollars per share)	$ 0.05			$ 0.03			$ 0.06	$ 0.01