Financial Instruments - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2017	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018	Apr. 30, 2018
Maximum
Financial Instrument [Line Items]
Derivative gains included in accumulated other comprehensive income				$ 600,000
Designated as Hedge Instrument | Interest Rate Swap | Cash Flow Hedge
Financial Instrument [Line Items]
Derivative notional amount	$ 129,800,000	$ 110,000,000		$ 110,000,000
Derivative, Maturity Date	Jun. 15, 2021
Interest rate		1.919%		1.919%
Not Designated as Hedge Instrument | Foreign Exchange Forward Contracts
Financial Instrument [Line Items]
Foreign currency gains (losses)		$ 700,000	$ (1,900,000)	$ 600,000	$ (4,200,000)
Not Designated as Hedge Instrument | Foreign Exchange Forward Contracts | Other Accrued Liabilities | Derivatives Purchased
Financial Instrument [Line Items]
Derivative notional amount		48,400,000		48,400,000		$ 80,800,000
Not Designated as Hedge Instrument | Foreign Exchange Forward Contracts | Other Accrued Liabilities | Derivatives Sold
Financial Instrument [Line Items]
Derivative notional amount		$ 45,900,000		$ 45,900,000		$ 78,500,000