Short-Term Investments - Schedule of Short-Term Investments (Detail) - USD ($) $ in Thousands	Apr. 30, 2021	Jan. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 963,023	$ 929,273
Gross unrealized gains	2,710	3,879
Gross unrealized losses	(280)	(30)
Estimated fair value	965,453	933,122
Certificates of deposits
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	22,350	17,350
Gross unrealized gains	18	15
Gross unrealized losses	0	(1)
Estimated fair value	22,368	17,364
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	144,412	125,833
Gross unrealized gains	470	745
Gross unrealized losses	(49)	(2)
Estimated fair value	144,833	126,576
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	59,425	57,390
Gross unrealized gains	4	8
Gross unrealized losses	(5)	(2)
Estimated fair value	59,424	57,396
Corporate notes and bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	535,609	428,710
Gross unrealized gains	1,743	2,360
Gross unrealized losses	(209)	(23)
Estimated fair value	537,143	431,047
Foreign government bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	32,092	31,855
Gross unrealized gains	41	45
Gross unrealized losses	(9)	(2)
Estimated fair value	32,124	31,898
U.S. agency obligations
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	52,761	52,756
Gross unrealized gains	78	119
Gross unrealized losses	0	0
Estimated fair value	52,839	52,875
U.S. treasury securities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	116,374	215,379
Gross unrealized gains	356	587
Gross unrealized losses	(8)	0
Estimated fair value	$ 116,722	$ 215,966