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Marketable Securities - Additional Information (Detail) $ in Thousands	12 Months Ended
	Jan. 31, 2021 USD ($) Security	Jan. 31, 2020 USD ($) Security	Jan. 31, 2019 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Sales and maturities of marketable securities	$ 396,260	$ 428,508	$ 267,072
Amortization of discounts and premiums, net	$ 1,574	$ 706	1,695
Total number of securities with unrealized loss positions within the Company's portfolio | Security	184	83
Interest income
Schedule of Available-for-sale Securities [Line Items]
Net realized gain (loss)	$ (419)	$ 39	$ (22)

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Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of cash inflow from sale, maturity, prepayment and call of 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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