Financial Instruments and Fair Value - Schedule of Cash Equivalents and Marketable Debt Securities (Detail) - USD ($) $ in Thousands	Jan. 31, 2021	Jan. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Total cash equivalents and marketable debt securities	$ 214,802	$ 211,081
Included in cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Total cash equivalents and marketable debt securities	15,368	37,736
Included in marketable debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total cash equivalents and marketable debt securities	$ 199,434	$ 173,345