Investments - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Jul. 31, 2025	Jan. 31, 2025
Marketable Securities [Line Items]
Amortized Cost	$ 6,581,361	$ 6,436,471
Gross Unrealized Gains	5,836	12,170
Gross Unrealized Losses	(7,124)	(6,312)
Estimated Fair Value	6,580,073	6,442,329
U.S. government agency securities
Marketable Securities [Line Items]
Amortized Cost	4,790,509	4,412,730
Gross Unrealized Gains	4,278	8,449
Gross Unrealized Losses	(5,400)	(5,249)
Estimated Fair Value	4,789,387	4,415,930
Agency bonds
Marketable Securities [Line Items]
Amortized Cost	992,384	1,173,518
Gross Unrealized Gains	436	1,609
Gross Unrealized Losses	(1,242)	(643)
Estimated Fair Value	991,578	1,174,484
Corporate and other debt securities
Marketable Securities [Line Items]
Amortized Cost	730,062	719,145
Gross Unrealized Gains	1,122	2,069
Gross Unrealized Losses	(453)	(419)
Estimated Fair Value	730,731	720,795
Treasury bills
Marketable Securities [Line Items]
Amortized Cost	65,443	110,237
Gross Unrealized Gains	0	43
Gross Unrealized Losses	(29)	(1)
Estimated Fair Value	65,414	110,279
Commercial paper
Marketable Securities [Line Items]
Amortized Cost	2,963	20,841
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 2,963	$ 20,841