Investments and Fair Value Measurements - Fair Value of Financial Assets (Details) - USD ($) $ in Thousands	Oct. 31, 2023	Jan. 31, 2023
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	$ 889,510	$ 1,376,053
U.S. Government and Agency Securities
Assets:
Cash and cash equivalents		59,706
Corporate Bonds
Assets:
Cash and cash equivalents	14,623
Commercial Paper
Assets:
Cash and cash equivalents	113,141
Estimate of Fair Value Measurement \| Recurring basis
Fair Value Measurements
Money market funds	94,983	316,943
Assets:
Cash and cash equivalents	222,747	376,649
Investments, current	761,746	1,316,347
Total	984,493	1,692,996
Estimate of Fair Value Measurement \| Recurring basis \| Level 1
Fair Value Measurements
Money market funds	94,983	316,943
Estimate of Fair Value Measurement \| Recurring basis \| Level 2
Fair Value Measurements
Money market funds	0	0
Estimate of Fair Value Measurement \| Recurring basis \| Level 3
Fair Value Measurements
Money market funds	0	0
U.S. Government and Agency Securities \| Investments, Current
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	230,273	1,121,155
U.S. Government and Agency Securities \| Estimate of Fair Value Measurement \| Recurring basis
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	230,273	1,180,861
U.S. Government and Agency Securities \| Estimate of Fair Value Measurement \| Recurring basis \| Level 1
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	0	0
U.S. Government and Agency Securities \| Estimate of Fair Value Measurement \| Recurring basis \| Level 2
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	230,273	1,180,861
U.S. Government and Agency Securities \| Estimate of Fair Value Measurement \| Recurring basis \| Level 3
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	0	0
Corporate Bonds \| Investments, Current
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	20,250	53,833
Corporate Bonds \| Estimate of Fair Value Measurement \| Recurring basis
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	34,873	53,833
Corporate Bonds \| Estimate of Fair Value Measurement \| Recurring basis \| Level 1
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	0	0
Corporate Bonds \| Estimate of Fair Value Measurement \| Recurring basis \| Level 2
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	34,873	53,833
Corporate Bonds \| Estimate of Fair Value Measurement \| Recurring basis \| Level 3
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	0	0
Commercial Paper \| Investments, Current
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	511,223	141,359
Commercial Paper \| Estimate of Fair Value Measurement \| Recurring basis
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	624,364	141,359
Commercial Paper \| Estimate of Fair Value Measurement \| Recurring basis \| Level 1
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	0	0
Commercial Paper \| Estimate of Fair Value Measurement \| Recurring basis \| Level 2
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	624,364	141,359
Commercial Paper \| Estimate of Fair Value Measurement \| Recurring basis \| Level 3
Fair Value Measurements
U.S. treasury securities, corporate bonds and commercial paper	$ 0	$ 0

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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