Investments - Summary Marketable Securities (Details) - USD ($) $ in Thousands	Jan. 31, 2024	Jan. 31, 2023
Marketable Securities [Line Items]
Amortized Cost	$ 5,403,503	$ 4,392,058
Gross Unrealized Gains	11,446	599
Gross Unrealized Losses	(10,716)	(66,821)
Estimated Fair Value	5,404,233	4,325,836
Commercial paper
Marketable Securities [Line Items]
Amortized Cost	41,564	77,701
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	41,564	77,701
Agency bonds
Marketable Securities [Line Items]
Amortized Cost	1,667,601	823,027
Gross Unrealized Gains	2,426	63
Gross Unrealized Losses	(3,344)	(12,440)
Estimated Fair Value	1,666,683	810,650
Corporate and other debt securities
Marketable Securities [Line Items]
Amortized Cost	663,122	555,354
Gross Unrealized Gains	1,161	385
Gross Unrealized Losses	(1,124)	(4,845)
Estimated Fair Value	663,159	550,894
U.S. government agency securities
Marketable Securities [Line Items]
Amortized Cost	3,003,224	2,910,572
Gross Unrealized Gains	7,859	150
Gross Unrealized Losses	(6,241)	(49,507)
Estimated Fair Value	3,004,842	2,861,215
Treasury bills
Marketable Securities [Line Items]
Amortized Cost	27,992	25,404
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(7)	(29)
Estimated Fair Value	$ 27,985	$ 25,376