Investments - Available-for-Sale Marketable Securities (Details) - USD ($) $ in Thousands	Jan. 31, 2021	Apr. 30, 2020	Jan. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	$ 960,122	$ 33,104	$ 50,343
Gross Unrealized Gains	15	425
Gross Unrealized Losses	0	0
Cash, cash equivalents and available-for-sale debt securities, amortized cost	1,064,157	222,708
Cash, cash equivalents and available-for-sale debt securities	1,064,172	223,133
Money market funds
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	900,292	10,260
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	158,366	11,489
Gross Unrealized Gains	11	11
Gross Unrealized Losses	0	0
Estimated Fair Value	158,377	11,500
Certificate of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,500	28,476
Gross Unrealized Gains	3	1
Gross Unrealized Losses	0	0
Estimated Fair Value	3,503	28,477
U.S. government agencies securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	0	9,995
Gross Unrealized Gains	0	79
Gross Unrealized Losses	0	0
Estimated Fair Value	0	10,074
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,999	94,242
Gross Unrealized Gains	1	155
Gross Unrealized Losses		0
Estimated Fair Value	2,000	94,397
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	0	68,246
Gross Unrealized Gains	0	179
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 0	$ 68,425

Cash, Cash Equivalents And Available-for-sale Debt Securities

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Cash, Cash Equivalents And Available-for-sale Debt Securities, Amortized Cost

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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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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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