Short-Term Investments - Schedule of Short-Term Investments (Detail) - USD ($) $ in Thousands	Jul. 31, 2021	Jan. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 1,196,636	$ 929,273
Gross unrealized gains	2,436	3,879
Gross unrealized losses	(287)	(30)
Estimated fair value	1,198,785	933,122
Certificates of deposits
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	22,350	17,350
Gross unrealized gains	17	15
Gross unrealized losses	0	(1)
Estimated fair value	22,367	17,364
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	165,792	125,833
Gross unrealized gains	389	745
Gross unrealized losses	(46)	(2)
Estimated fair value	166,135	126,576
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	83,982	57,390
Gross unrealized gains	15	8
Gross unrealized losses	(2)	(2)
Estimated fair value	83,995	57,396
Corporate notes and bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	640,441	428,710
Gross unrealized gains	1,656	2,360
Gross unrealized losses	(226)	(23)
Estimated fair value	641,871	431,047
Foreign government bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	29,570	31,855
Gross unrealized gains	41	45
Gross unrealized losses	(6)	(2)
Estimated fair value	29,605	31,898
U.S. agency obligations
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	39,766	52,756
Gross unrealized gains	75	119
Gross unrealized losses	0	0
Estimated fair value	39,841	52,875
U.S. treasury securities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	214,735	215,379
Gross unrealized gains	243	587
Gross unrealized losses	(7)	0
Estimated fair value	$ 214,971	$ 215,966