Stockholders' Equity - Share Based Compensation Stock Options Activity (Detail) - $ / shares	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Shares
Options outstanding, beginning of year, Shares	267,761	316,160	335,160
Exercised during the period, Shares	(67,094)	(48,399)	(19,000)
Options outstanding, end of period, Shares	200,667	267,761	316,160
Weighted average remaining contractual life	5 months 4 days	2 years 4 months 6 days	3 years 1 month 28 days
Options exercisable, end of period, Shares	200,667	267,761	316,160
Weighted average remaining contractual life	5 months 4 days	2 years 4 months 6 days	3 years 1 month 28 days
Weighted-Average Exercise Price
Options outstanding, beginning of year, Weighted-Average Exercise Price	$ 6.76	$ 6.69	$ 6.58
Exercised during period, Weighted-Average Exercise Price	3.97	6.28	4.70
Options outstanding, end of period, Weighted-Average Exercise Price	7.70	6.76	6.69
Options exercisable, end of period, Weighted-Average Exercise Price	$ 7.70	$ 6.76	$ 6.69