Concentration of Risk (Details) - Customer Concentration Risk	3 Months Ended
	Jul. 31, 2021	Jul. 31, 2020
Customer receivables | Customer A
Concentration Risk [Line Items]
Concentration risk (as a percent)	31.20%	29.00%
Customer receivables | Customer B
Concentration Risk [Line Items]
Concentration risk (as a percent)	19.60%	25.10%
Sales revenue, gross | Customer A
Concentration Risk [Line Items]
Concentration risk (as a percent)	31.80%	27.70%
Sales revenue, gross | Customer B
Concentration Risk [Line Items]
Concentration risk (as a percent)	15.50%	16.90%