Significant Accounting Policies - Calculation of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Jul. 31, 2019	Jul. 31, 2018
Basic loss per share computation
Net income (loss) attributable to common stockholders	$ (641)	$ 482
Weighted Average common shares - basic (in shares)	11,619,538	11,012,281
Basic net income (loss) per share (in dollars per share)	$ (0.06)	$ 0.04
Income (loss) available to common stockholders	$ (641)	$ 482
Incremental shares from assumed exercise of warrants and stock options (in shares)	0	1,605,740
Adjusted weighted average share - diluted (in shares)	11,619,538	12,618,021
Diluted net income (loss) per share (in usd per share)	$ (0.06)	$ 0.04