Fair Value Measurements - Schedule of Financial Assets and Liabilities (Details) - USD ($)	3 Months Ended	9 Months Ended
	Oct. 31, 2022	Oct. 31, 2022	Oct. 31, 2021	Jan. 31, 2022
Short-term investments:
Unrealized losses		$ 3,500,000
Fair value of security owned not readily marketable	$ 9,300,000	9,300,000		$ 4,800,000
Payments To Acquire Non Marketable Securities	1,600,000	2,723,000	$ 2,343,000
Gain on non-marketable securities		(1,694,000)	$ 0
Fair Value, Recurring
Short-term investments:
Total financial assets	1,633,170,000	1,633,170,000		1,683,240,000
Level 1 | Fair Value, Recurring
Short-term investments:
Total financial assets	1,633,170,000	1,633,170,000		1,683,240,000
Level 2 | Fair Value, Recurring
Short-term investments:
Total financial assets	0	0		0
Level 3 | Fair Value, Recurring
Short-term investments:
Total financial assets	0	0		0
U.S. government treasury securities | Fair Value, Recurring
Short-term investments:
Short-term investments:	787,858,000	787,858,000		1,352,019,000
U.S. government treasury securities | Level 1 | Fair Value, Recurring
Short-term investments:
Short-term investments:	787,858,000	787,858,000		1,352,019,000
U.S. government treasury securities | Level 2 | Fair Value, Recurring
Short-term investments:
Short-term investments:	0	0		0
U.S. government treasury securities | Level 3 | Fair Value, Recurring
Short-term investments:
Short-term investments:	0	0		0
Money market funds | Fair Value, Recurring
Cash and cash equivalents:
Cash and cash equivalents:	845,312,000	845,312,000		331,221,000
Money market funds | Level 1 | Fair Value, Recurring
Cash and cash equivalents:
Cash and cash equivalents:	845,312,000	845,312,000		331,221,000
Money market funds | Level 2 | Fair Value, Recurring
Cash and cash equivalents:
Cash and cash equivalents:	0	0		0
Money market funds | Level 3 | Fair Value, Recurring
Cash and cash equivalents:
Cash and cash equivalents:	$ 0	$ 0		$ 0