Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Apr. 30, 2021	Apr. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and available-for-sale marketable securities	$ 1,021,421	$ 223,133
U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	57,998	11,500
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	422,978	28,477
U.S. government agencies securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	0	10,074
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	494,676	94,397
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	2,368	68,425
Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and available-for-sale marketable securities	1,021,421	223,133
Fair Value, Recurring | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	43,401	10,260
Fair Value, Recurring | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	57,998	11,500
Fair Value, Recurring | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	422,978	28,477
Fair Value, Recurring | U.S. government agencies securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	0	10,074
Fair Value, Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	494,676	94,397
Fair Value, Recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	2,368	68,425
Fair Value, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and available-for-sale marketable securities	43,401	10,260
Fair Value, Recurring | Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	43,401	10,260
Fair Value, Recurring | Level 1 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	0	0
Fair Value, Recurring | Level 1 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	0	0
Fair Value, Recurring | Level 1 | U.S. government agencies securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	0	0
Fair Value, Recurring | Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	0	0
Fair Value, Recurring | Level 1 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	0	0
Fair Value, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and available-for-sale marketable securities	978,020	212,873
Fair Value, Recurring | Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Recurring | Level 2 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	57,998	11,500
Fair Value, Recurring | Level 2 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	422,978	28,477
Fair Value, Recurring | Level 2 | U.S. government agencies securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	0	10,074
Fair Value, Recurring | Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	494,676	94,397
Fair Value, Recurring | Level 2 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	2,368	68,425
Fair Value, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and available-for-sale marketable securities	0	0
Fair Value, Recurring | Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Recurring | Level 3 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	0	0
Fair Value, Recurring | Level 3 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	0	0
Fair Value, Recurring | Level 3 | U.S. government agencies securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	0	0
Fair Value, Recurring | Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	0	0
Fair Value, Recurring | Level 3 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale marketable securities	$ 0	$ 0