Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jul. 31, 2021	Apr. 30, 2021
Available-for-sale marketable securities:
Total cash equivalents and available-for-sale marketable securities	$ 1,006,659	$ 1,021,421
Commercial paper
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	430,191	494,676
Corporate debt securities
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	24,156	2,368
U.S. treasury securities
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	1,999	57,998
Certificates of deposit
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	368,865	422,978
Fair Value, Recurring
Available-for-sale marketable securities:
Total cash equivalents and available-for-sale marketable securities	1,006,659	1,021,421
Fair Value, Recurring | Money market funds
Cash equivalents:
Cash equivalents, fair value	175,998	43,401
Fair Value, Recurring | Commercial paper
Cash equivalents:
Cash equivalents, fair value	5,400	0
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	430,191	494,676
Fair Value, Recurring | Corporate debt securities
Cash equivalents:
Cash equivalents, fair value	50	0
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	24,156	2,368
Fair Value, Recurring | U.S. treasury securities
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	1,999	57,998
Fair Value, Recurring | Certificates of deposit
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	368,865	422,978
Fair Value, Recurring | Level 1
Available-for-sale marketable securities:
Total cash equivalents and available-for-sale marketable securities	175,998	43,401
Fair Value, Recurring | Level 1 | Money market funds
Cash equivalents:
Cash equivalents, fair value	175,998	43,401
Fair Value, Recurring | Level 1 | Commercial paper
Cash equivalents:
Cash equivalents, fair value	0	0
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	0	0
Fair Value, Recurring | Level 1 | Corporate debt securities
Cash equivalents:
Cash equivalents, fair value	0	0
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	0	0
Fair Value, Recurring | Level 1 | U.S. treasury securities
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	0	0
Fair Value, Recurring | Level 1 | Certificates of deposit
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	0	0
Fair Value, Recurring | Level 2
Available-for-sale marketable securities:
Total cash equivalents and available-for-sale marketable securities	830,661	978,020
Fair Value, Recurring | Level 2 | Money market funds
Cash equivalents:
Cash equivalents, fair value	0	0
Fair Value, Recurring | Level 2 | Commercial paper
Cash equivalents:
Cash equivalents, fair value	5,400	0
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	430,191	494,676
Fair Value, Recurring | Level 2 | Corporate debt securities
Cash equivalents:
Cash equivalents, fair value	50	0
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	24,156	2,368
Fair Value, Recurring | Level 2 | U.S. treasury securities
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	1,999	57,998
Fair Value, Recurring | Level 2 | Certificates of deposit
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	368,865	422,978
Fair Value, Recurring | Level 3
Available-for-sale marketable securities:
Total cash equivalents and available-for-sale marketable securities	0	0
Fair Value, Recurring | Level 3 | Money market funds
Cash equivalents:
Cash equivalents, fair value	0	0
Fair Value, Recurring | Level 3 | Commercial paper
Cash equivalents:
Cash equivalents, fair value	0	0
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	0	0
Fair Value, Recurring | Level 3 | Corporate debt securities
Cash equivalents:
Cash equivalents, fair value	0	0
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	0	0
Fair Value, Recurring | Level 3 | U.S. treasury securities
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	0	0
Fair Value, Recurring | Level 3 | Certificates of deposit
Available-for-sale marketable securities:
Available-for-sale marketable securities, fair value	$ 0	$ 0