Investments - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Apr. 30, 2022	Jan. 31, 2022
Marketable Securities [Line Items]
Amortized Cost	$ 4,378,899	$ 4,380,350
Gross Unrealized Gains	46	35
Gross Unrealized Losses	(59,971)	(23,939)
Estimated Fair Value	4,318,974	4,356,446
Commercial paper
Marketable Securities [Line Items]
Amortized Cost	34,881	28,723
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	34,881	28,723
Agency bonds
Marketable Securities [Line Items]
Amortized Cost	604,439	632,935
Gross Unrealized Gains	1	2
Gross Unrealized Losses	(10,043)	(3,328)
Estimated Fair Value	594,397	629,609
Corporate and other debt securities
Marketable Securities [Line Items]
Amortized Cost	288,312	282,124
Gross Unrealized Gains	1	5
Gross Unrealized Losses	(3,062)	(1,202)
Estimated Fair Value	285,251	280,927
U.S. government agency securities
Marketable Securities [Line Items]
Amortized Cost	3,192,672	3,046,742
Gross Unrealized Gains	43	28
Gross Unrealized Losses	(46,657)	(19,261)
Estimated Fair Value	3,146,058	3,027,509
Treasury bills
Marketable Securities [Line Items]
Amortized Cost	258,595	389,826
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(209)	(148)
Estimated Fair Value	$ 258,387	$ 389,678

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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