Financial Instruments and Fair Value - Schedule of Available-for-Sale Securities at Fair Value (Detail) - USD ($) $ in Thousands	Jan. 31, 2021	Jan. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 213,583	$ 210,313
Unrealized Gains	1,226	770
Unrealized Losses	(7)	(2)
Fair Value	214,802	211,081
Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	171	8,284
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	171	8,284
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	66,181	63,390
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	66,181	63,390
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	102,108	95,053
Unrealized Gains	980	653
Unrealized Losses	(7)	0
Fair Value	103,081	95,706
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,740	23,062
Unrealized Gains	164	69
Unrealized Losses	0	(2)
Fair Value	15,904	23,129
U.S. government securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	29,383	20,524
Unrealized Gains	82	48
Unrealized Losses	0	0
Fair Value	$ 29,465	$ 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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