Revenue Recognition - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020	Apr. 30, 2020
Revenue Recognition [Line Items]
Amounts received for reimbursement of travel and other out-of-pocket expenses	$ 0	$ 400,000	$ 16,000	$ 1,300,000
Deferred revenue recognized	15,000,000		30,900,000
Transaction price allocated to remaining performance obligations	80,000,000.0		80,000,000.0
Total deferred commissions	32,023,000		32,023,000		$ 34,227,000
Impairment losses	0		0
Sales Commissions
Revenue Recognition [Line Items]
Total deferred commissions	3,000,000.0		3,000,000.0		$ 3,500,000
Amortization of sales commissions	$ 500,000		$ 1,400,000
Minimum
Revenue Recognition [Line Items]
Contractual period of maintenance contract			1 year
Maximum
Revenue Recognition [Line Items]
Contractual period of maintenance contract			3 years