Revenue Recognition - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Apr. 30, 2020
Revenue Recognition [Line Items]
Amounts received for reimbursement of travel and other out-of-pocket expenses	$ 12,000	$ 500,000	$ 16,000	$ 900,000
Deferred revenue recognized	14,600,000		25,000,000
Transaction price allocated to remaining performance obligations	78,000,000.0		78,000,000.0
Total deferred commissions	31,206,000		31,206,000		$ 34,227,000
Impairment losses	0		0
Sales Commissions
Revenue Recognition [Line Items]
Total deferred commissions	3,100,000		3,100,000		$ 3,500,000
Amortization of sales commissions	$ 500,000		$ 900,000
Minimum
Revenue Recognition [Line Items]
Contractual period of maintenance contract			1 year
Maximum
Revenue Recognition [Line Items]
Contractual period of maintenance contract			3 years