Fair Value Measurements - Fair Value Hierarchy for Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Apr. 30, 2021	Jan. 31, 2021
Assets
Short-term investments	$ 965,453	$ 933,122
Fair value, measurements recurring
Assets
Total financial assets	1,617,564	1,209,019
Liabilities
Total financial liabilities		72
Fair value, measurements recurring \| Money market funds
Assets
Cash equivalents:	626,523	259,937
Fair value, measurements recurring \| Commercial paper
Assets
Cash equivalents:	22,949
Short-term investments	59,424	57,396
Fair value, measurements recurring \| Corporate notes and bonds
Assets
Cash equivalents:	2,630
Short-term investments	537,143	431,047
Fair value, measurements recurring \| U.S. treasury securities
Assets
Cash equivalents:		15,520
Short-term investments	116,722	215,966
Fair value, measurements recurring \| Certificates of deposits
Assets
Short-term investments	22,368	17,364
Fair value, measurements recurring \| Asset-backed securities
Assets
Short-term investments	144,833	126,576
Fair value, measurements recurring \| Foreign government bonds
Assets
Short-term investments	32,124	31,898
Fair value, measurements recurring \| U.S. agency obligations
Assets
Short-term investments	52,839	52,875
Fair value, measurements recurring \| Foreign currency derivative contracts
Assets
Short-term investments	9	440
Fair value, measurements recurring \| Foreign currency derivative contracts
Liabilities
Foreign currency derivative contracts		72
Fair value, measurements recurring \| Level 1
Assets
Total financial assets	626,523	259,937
Liabilities
Total financial liabilities		0
Fair value, measurements recurring \| Level 1 \| Money market funds
Assets
Cash equivalents:	626,523	259,937
Fair value, measurements recurring \| Level 1 \| Commercial paper
Assets
Cash equivalents:	0
Short-term investments	0	0
Fair value, measurements recurring \| Level 1 \| Corporate notes and bonds
Assets
Cash equivalents:	0
Short-term investments	0	0
Fair value, measurements recurring \| Level 1 \| U.S. treasury securities
Assets
Cash equivalents:		0
Short-term investments	0	0
Fair value, measurements recurring \| Level 1 \| Certificates of deposits
Assets
Short-term investments	0	0
Fair value, measurements recurring \| Level 1 \| Asset-backed securities
Assets
Short-term investments	0	0
Fair value, measurements recurring \| Level 1 \| Foreign government bonds
Assets
Short-term investments	0	0
Fair value, measurements recurring \| Level 1 \| U.S. agency obligations
Assets
Short-term investments	0	0
Fair value, measurements recurring \| Level 1 \| Foreign currency derivative contracts
Assets
Short-term investments	0	0
Fair value, measurements recurring \| Level 1 \| Foreign currency derivative contracts
Liabilities
Foreign currency derivative contracts		0
Fair value, measurements recurring \| Level 2
Assets
Total financial assets	991,041	949,082
Liabilities
Total financial liabilities		72
Fair value, measurements recurring \| Level 2 \| Money market funds
Assets
Cash equivalents:	0	0
Fair value, measurements recurring \| Level 2 \| Commercial paper
Assets
Cash equivalents:	22,949
Short-term investments	59,424	57,396
Fair value, measurements recurring \| Level 2 \| Corporate notes and bonds
Assets
Cash equivalents:	2,630
Short-term investments	537,143	431,047
Fair value, measurements recurring \| Level 2 \| U.S. treasury securities
Assets
Cash equivalents:		15,520
Short-term investments	116,722	215,966
Fair value, measurements recurring \| Level 2 \| Certificates of deposits
Assets
Short-term investments	22,368	17,364
Fair value, measurements recurring \| Level 2 \| Asset-backed securities
Assets
Short-term investments	144,833	126,576
Fair value, measurements recurring \| Level 2 \| Foreign government bonds
Assets
Short-term investments	32,124	31,898
Fair value, measurements recurring \| Level 2 \| U.S. agency obligations
Assets
Short-term investments	52,839	52,875
Fair value, measurements recurring \| Level 2 \| Foreign currency derivative contracts
Assets
Short-term investments	$ 9	440
Fair value, measurements recurring \| Level 2 \| Foreign currency derivative contracts
Liabilities
Foreign currency derivative contracts		$ 72

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), classified as current.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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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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Fair value as of the balance sheet date of all foreign currency derivative liabilities not designated as hedging instruments.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Fair value of financial and nonfinancial obligations.

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