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Financial Instruments - Additional Information (Details) - USD ($) | 3 Months Ended |
--- | --- | ---
Apr. 30, 2021 | Apr. 30, 2020 | Jan. 31, 2021
Investments, All Other Investments [Abstract] |  |  |
Securities in a continuous unrealized loss position for more than 12 months | $ 0 |  | $ 0
Allowance for credit loss | 0 | $ 0 |
Securities, writeoff | 0 | 0 |
Gain (loss) from sale or redemption of available for sale securities | 0 | 0 |
Sales and maturities of marketable securities | 4,000,000.0 | $ 0 |
Direct investments in privately held companies | 129,800,000 |  | $ 134,100,000
Equity method investment, realized gain (loss) on disposal | $ 8,100,000 |  |

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