Financial Instruments and Fair Value - Schedule of Available-for-Sale Securities at Fair Value (Detail) - USD ($) $ in Thousands	Oct. 31, 2020	Jan. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 213,047	$ 210,313
Unrealized Gains	1,384	770
Unrealized Losses	(21)	(2)
Fair Value	214,410	211,081
Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,384	8,284
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	2,384	8,284
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	66,744	63,390
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	66,744	63,390
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	101,102	95,053
Unrealized Gains	1,093	653
Unrealized Losses	(21)	0
Fair Value	102,174	95,706
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,391	23,062
Unrealized Gains	212	69
Unrealized Losses	0	(2)
Fair Value	16,603	23,129
U.S. government securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	26,426	20,524
Unrealized Gains	79	48
Unrealized Losses	0	0
Fair Value	$ 26,505	$ 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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