Financial Instruments - Financial Instruments and Balance Sheet Classification (Detail) - USD ($) $ in Thousands		Apr. 30, 2021	Apr. 30, 2020
Investment Holdings [Line Items]
Cash and cash equivalents		$ 850,778	$ 689,244
Marketable Securities, Current		63,667	41,951
Marketable securities, non-current		182,692	132,134
Other Accrued Liabilities		(12)
Income Taxes & Other Receivables			2,634
Fair Value		1,097,125	865,963
Fair Value, Inputs, Level 2
Investment Holdings [Line Items]
Cost		80,325	38,313
Unrealized Gains		1	65
Unrealized Losses		(27)	(19)
Fair Value		80,299	38,359
Cash and cash equivalents		9,499	5,686
Marketable Securities, Current		54,583	32,673
Marketable securities, non-current		16,217
Fair Value, Inputs, Level 2 | Commercial Paper
Investment Holdings [Line Items]
Cost		51,979	19,132
Unrealized Gains		1	39
Unrealized Losses		(7)
Fair Value		51,973	19,171
Cash and cash equivalents		9,499	4,785
Marketable Securities, Current		42,474	14,386
Fair Value, Inputs, Level 2 | Corporate Notes/Bonds
Investment Holdings [Line Items]
Cost		26,371	19,181
Unrealized Gains			26
Unrealized Losses		(20)	(19)
Fair Value		26,351	19,188
Cash and cash equivalents			901
Marketable Securities, Current		10,134	18,287
Marketable securities, non-current		16,217
Fair Value, Inputs, Level 2 | U.S. Treasury and Agency Securities
Investment Holdings [Line Items]
Cost		1,975
Fair Value		1,975
Marketable Securities, Current		1,975
Fair Value, Inputs, Level 2 | Foreign Exchange Forward Contracts
Investment Holdings [Line Items]
Other Accrued Liabilities		(12)
Income Taxes & Other Receivables			2,634
Fair Value		(12)	2,634
Fair Value, Inputs, Level 1 | Mutual Funds
Investment Holdings [Line Items]
Marketable Securities, Current	[1]	9,084	9,278
Marketable securities, non-current	[1]	166,475	132,134
Fair Value	[1]	175,559	141,412
Fair Value, Inputs, Level 1 | Equity Securities
Investment Holdings [Line Items]
Marketable Securities, Current		9,084	9,278
Marketable securities, non-current		166,475	132,134
Fair Value		175,559	141,412
Fair Value, Inputs, Level 1 | Cash
Investment Holdings [Line Items]
Cash and cash equivalents		752,737	611,795
Fair Value		752,737	611,795
Fair Value, Inputs, Level 1 | Money Market Funds
Investment Holdings [Line Items]
Cash and cash equivalents		88,542	71,763
Fair Value		$ 88,542	$ 71,763

[1] These investments are held in trust for settlement of the Company’s vested obligations of $157.3 million and $124.6 million as of April 30, 2021 and 2020, respectively, under the ECAP (see Note 6 — Deferred Compensation and Retirement Plans). Unvested obligations under the deferred compensation plans totaled $26.5 million and $21.7 million as of April 30, 2021 and 2020, respectively. During fiscal 2021 and 2019, the fair value of the investments increased; therefore, the Company recognized income of $38.5 million and $8.1 million, respectively, which was recorded in other income (loss), net. During fiscal 2020, the fair value of the investments decreased; therefore, the Company recognized a loss of $1.8 million which was recorded in other income (loss), net.