Financial Instruments and Fair Value - Schedule of Available-for-Sale Securities at Fair Value (Detail) - USD ($) $ in Thousands	Jul. 31, 2020	Jan. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 212,429	$ 210,313
Unrealized Gains	1,631	770
Unrealized Losses	(44)	(2)
Fair Value	214,016	211,081
Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	164	8,284
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	164	8,284
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	61,621	63,390
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	61,621	63,390
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	96,410	95,053
Unrealized Gains	1,274	653
Unrealized Losses	(44)	0
Fair Value	97,640	95,706
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,904	23,062
Unrealized Gains	240	69
Unrealized Losses	0	(2)
Fair Value	20,144	23,129
U.S. government securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	34,330	20,524
Unrealized Gains	117	48
Unrealized Losses	0	0
Fair Value	$ 34,447	$ 20,572

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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