Marketable Securities - Summary of Available-for-sale Marketable Securities Excluding Securities Classified within Cash and Cash Equivalents on Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Apr. 30, 2021	Jan. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Costs	$ 237,737	$ 282,908
Unrealized Gains	100	129
Unrealized Losses	(1)	(1)
Fair Value	237,836	283,036
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Costs	227,010	268,141
Unrealized Gains	57	29
Unrealized Losses	(1)	(1)
Fair Value	227,066	268,169
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Costs	10,447	14,487
Unrealized Gains	43	100
Unrealized Losses	0	0
Fair Value	10,490	14,587
Certificate of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Costs	280	280
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	$ 280	$ 280