Revenue Recognition - Additional Information (Detail) - USD ($)	3 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Apr. 30, 2018
Revenue Recognition [Line Items]
Amounts received for reimbursement of travel and other out-of-pocket expenses	$ 27,399,000	$ 26,886,000
Transaction price allocated to remaining performance obligations	$ 54,000,000
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months
Total deferred commissions	$ 2,400,000		$ 2,500,000
Amortization of sales commissions	$ 200,000
Minimum
Revenue Recognition [Line Items]
Contractual period of maintenance contract	1 year
Maximum
Revenue Recognition [Line Items]
Contractual period of maintenance contract	3 years
Reimbursement
Revenue Recognition [Line Items]
Amounts received for reimbursement of travel and other out-of-pocket expenses	$ 331,000	$ 525,000