Long-Term Debt - Schedule of Long-term Debt, at Amortized Cost (Detail) - USD ($) $ in Thousands	Jul. 31, 2020	Apr. 30, 2020
Debt Instrument [Line Items]
Long-term borrowings, net of unamortized discount and debt issuance costs	$ 394,303	$ 394,144
4.625% Senior Unsecured Notes due 2027
Debt Instrument [Line Items]
Less: Unamortized discount and issuance costs	(5,697)	(5,856)
Long-term borrowings, net of unamortized discount and debt issuance costs	394,303	394,144
4.625% Senior Unsecured Notes due 2027 | Senior Unsecured Notes
Debt Instrument [Line Items]
Long-term debt	$ 400,000	$ 400,000