Marketable Securities - Summary of Fair Value of Company's Investment By Type (Detail) - USD ($) $ in Thousands	Apr. 30, 2021	Apr. 30, 2020
Marketable Securities [Line Items]
Amortized Cost	$ 198,536	$ 51,456
Unrealized Gains	62	470
Unrealized Losses	(261)	(1)
Fair Value	198,337	51,925
Corporate Debt Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	158,063	38,922
Unrealized Gains	55	295
Unrealized Losses	(245)	(1)
Fair Value	157,873	39,216
Obligations of U.S. Government and Its Agencies [Member]
Marketable Securities [Line Items]
Amortized Cost	40,473	12,534
Unrealized Gains	7	175
Unrealized Losses	(16)
Fair Value	$ 40,464	$ 12,709

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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