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Marketable Securities - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Oct. 31, 2021 | Oct. 31, 2020 | Oct. 31, 2021 | Oct. 31, 2020
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Sales and maturities of marketable securities |  |  | $ 237,879 | $ 384,999
Amortization of discounts and premiums, net | $ 1,804 | $ 201 | 4,540 | 818
Other (Loss) Income, Net |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Net realized gain (loss) | $ 9 | $ 1 | $ 13 | $ (419)

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