Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands | Jan. 31, 2021 | Apr. 30, 2020 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash, cash equivalents and available-for-sale debt securities | $ 1,064,172 | $ 223,133 |
U.S. treasury securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available-for-sale marketable securities | 158,377 | 11,500 |
Certificate of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available-for-sale marketable securities | 3,503 | 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 | 2,000 | 94,397 |
Corporate debt securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available-for-sale marketable securities | 0 | 68,425 |
Fair Value, Recurring | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash, cash equivalents and available-for-sale debt securities | 1,064,172 | 223,133 |
Fair Value, Recurring | Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash and cash equivalents, fair value | 900,292 | 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 | 158,377 | 11,500 |
Fair Value, Recurring | Certificate of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available-for-sale marketable securities | 3,503 | 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 | 2,000 | 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 | 0 | 68,425 |
Fair Value, Recurring | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash, cash equivalents and available-for-sale debt securities | 900,292 | 10,260 |
Fair Value, Recurring | Level 1 | Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash and cash equivalents, fair value | 900,292 | 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 | Certificate 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] | | |
Cash, cash equivalents and available-for-sale debt securities | 163,880 | 212,873 |
Fair Value, Recurring | Level 2 | Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash and cash equivalents, fair value | 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 | 158,377 | 11,500 |
Fair Value, Recurring | Level 2 | Certificate of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available-for-sale marketable securities | 3,503 | 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 | 2,000 | 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 | 0 | 68,425 |
Fair Value, Recurring | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash, cash equivalents and available-for-sale debt 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 and cash equivalents, fair value | 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 | Certificate 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 |