Fair Value Measurements - Schedule of Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings (Details) - USD ($)	Jul. 31, 2020	Apr. 30, 2020	Jul. 31, 2019	Apr. 30, 2019
Assets
Cash, carrying amount	$ 2,674,216	$ 2,433,266	$ 1,223,953	$ 1,862,458
Cash, fair value	2,674,216	2,433,266
Foreign currency option contracts, carrying amount		6,381
Foreign currency option contracts, fair value		6,381
Foreign currency forward contracts, carrying amount	26,398
Foreign currency forward contracts, fair value	26,398
Assets, carrying amount	2,700,614	2,439,647
Assets, fair value	2,700,614	2,439,647
Liabilities
Foreign currency option contracts, carrying amount	0	140,299
Foreign currency option contracts, fair value	$ 0	$ 140,399