Investments - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Oct. 31, 2021	Jan. 31, 2021
Marketable Securities [Line Items]
Amortized Cost	$ 4,100,639	$ 2,003,560
Gross Unrealized Gains	86	1,226
Gross Unrealized Losses	(5,205)	(376)
Estimated Fair Value	4,095,520	2,004,410
Commercial paper
Marketable Securities [Line Items]
Amortized Cost	23,482	26,222
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	23,482	26,222
Agency bonds
Marketable Securities [Line Items]
Amortized Cost	437,782	461,335
Gross Unrealized Gains	13	79
Gross Unrealized Losses	(342)	(49)
Estimated Fair Value	437,453	461,365
Corporate and other debt securities
Marketable Securities [Line Items]
Amortized Cost	314,888	465,207
Gross Unrealized Gains	56	1,113
Gross Unrealized Losses	(423)	(64)
Estimated Fair Value	314,521	466,256
U.S. government agency securities
Marketable Securities [Line Items]
Amortized Cost	3,000,441	834,894
Gross Unrealized Gains	17	28
Gross Unrealized Losses	(4,413)	(257)
Estimated Fair Value	2,996,045	834,665
Treasury bills
Marketable Securities [Line Items]
Amortized Cost	324,046	215,902
Gross Unrealized Gains	0	6
Gross Unrealized Losses	(27)	(6)
Estimated Fair Value	$ 324,019	$ 215,902

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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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