Fair Value Measurements - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Oct. 31, 2021	Oct. 31, 2021	Oct. 31, 2020	Jan. 31, 2021
Short-term investments:
Total financial assets	$ 1,686,670	$ 1,686,670		$ 858,154
Other assets	110,106	110,106		85,555
Investment in non-marketable securities	(1,200)	(2,343)	$ (500)
Variable Interest Entity, Not Primary Beneficiary
Short-term investments:
Other assets	2,800	2,800		500
Level 1
Short-term investments:
Total financial assets	1,686,670	1,686,670		858,154
Level 2
Short-term investments:
Total financial assets	0	0		0
Level 3
Short-term investments:
Total financial assets	0	0		0
U.S. government treasury securities
Short-term investments:
Short-term investments:	1,054,746	1,054,746		528,045
U.S. government treasury securities | Level 1
Short-term investments:
Short-term investments:	1,054,746	1,054,746		528,045
U.S. government treasury securities | Level 2
Short-term investments:
Short-term investments:	0	0		0
U.S. government treasury securities | Level 3
Short-term investments:
Short-term investments:	0	0		0
Money market funds
Cash and cash equivalents:
Cash and cash equivalents:	631,924	631,924		330,109
Money market funds | Level 1
Cash and cash equivalents:
Cash and cash equivalents:	631,924	631,924		330,109
Money market funds | Level 2
Cash and cash equivalents:
Cash and cash equivalents:	0	0		0
Money market funds | Level 3
Cash and cash equivalents:
Cash and cash equivalents:	$ 0	$ 0		$ 0