Financial Instruments - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017	Apr. 30, 2018
Maximum
Financial Instrument [Line Items]
Derivative gains included in accumulated other comprehensive income				$ 800,000
Designated as Hedge Instrument | Interest Rate Swap | Cash Flow Hedge
Financial Instrument [Line Items]
Derivative notional amount	$ 129,800,000	$ 113,400,000		$ 113,400,000
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)		$ (200,000)	$ 300,000	$ (100,000)	$ (2,300,000)
Not Designated as Hedge Instrument | Foreign Exchange Forward Contracts | Other Accrued Liabilities | Derivatives Purchased
Financial Instrument [Line Items]
Derivative notional amount		36,400,000		36,400,000		$ 80,800,000
Not Designated as Hedge Instrument | Foreign Exchange Forward Contracts | Other Accrued Liabilities | Derivatives Sold
Financial Instrument [Line Items]
Derivative notional amount		$ 49,600,000		$ 49,600,000		$ 78,500,000