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Marketable Securities (Tables) | 6 Months Ended
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Jul. 31, 2021
Investments Debt And Equity Securities [Abstract] |
Amortized Cost, Gross Unrealized Gains (Losses) and Fair Value of Available-For-Sale Securities | The amortized cost, gross unrealized gains (losses) and fair value of available-for-sale securities by major security type and class of security as of July 31, 2021, January 31, 2021 and July 31, 2020 were as follows:
|  | Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Fair |
|  | Cost |  |  | Gains |  |  | (Losses) |  |  | Value |
As of July 31, 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Municipal and pre-refunded municipal bonds |  | $ | 122,173 |  |  | $ | 14 |  |  | $ | (87 | ) |  | $ | 122,100 |
Corporate bonds |  |  | 28,808 |  |  |  | 2 |  |  |  | (24 | ) |  |  | 28,786 |
Commercial paper |  |  | 6,096 |  |  |  | — |  |  |  | — |  |  |  | 6,096 |
|  |  | 157,077 |  |  |  | 16 |  |  |  | (111 | ) |  |  | 156,982 |
Long-term Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Municipal and pre-refunded municipal bonds |  |  | 40,069 |  |  |  | 34 |  |  |  | (56 | ) |  | $ | 40,047 |
Corporate bonds |  |  | 61,646 |  |  |  | 4 |  |  |  | (159 | ) |  |  | 61,491 |
Mutual funds, held in rabbi trust |  |  | 11,610 |  |  |  | 143 |  |  |  | (42 | ) |  |  | 11,711 |
|  |  | 113,325 |  |  |  | 181 |  |  |  | (257 | ) |  |  | 113,249 |
|  | $ | 270,402 |  |  | $ | 197 |  |  | $ | (368 | ) |  | $ | 270,231 |
As of January 31, 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Municipal and pre-refunded municipal bonds |  | $ | 127,097 |  |  | $ | 11 |  |  | $ | (53 | ) |  | $ | 127,055 |
Corporate bonds |  |  | 38,695 |  |  |  | 1 |  |  |  | (48 | ) |  |  | 38,648 |
Commercial paper |  |  | 8,992 |  |  |  | — |  |  |  | — |  |  |  | 8,992 |
|  |  | 174,784 |  |  |  | 12 |  |  |  | (101 | ) |  |  | 174,695 |
Long-term Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Municipal and pre-refunded municipal bonds |  |  | 53,134 |  |  |  | 17 |  |  |  | (46 | ) |  |  | 53,105 |
Corporate bonds |  |  | 59,890 |  |  |  | 3 |  |  |  | (129 | ) |  |  | 59,764 |
Mutual funds, held in rabbi trust |  |  | 10,827 |  |  |  | 20 |  |  |  | (54 | ) |  |  | 10,793 |
|  |  | 123,851 |  |  |  | 40 |  |  |  | (229 | ) |  |  | 123,662 |
|  | $ | 298,635 |  |  | $ | 52 |  |  | $ | (330 | ) |  | $ | 298,357 |
|  | Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Fair |
|  | Cost |  |  | Gains |  |  | (Losses) |  |  | Value |
As of July 31, 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Municipal and pre-refunded municipal bonds |  | $ | 210 |  |  | $ | — |  |  | $ | — |  |  | $ | 210 |
Corporate bonds |  |  | 291 |  |  |  | — |  |  |  | — |  |  |  | 291 |
|  |  | 501 |  |  |  | — |  |  |  | — |  |  |  | 501 |
Long-term Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Municipal and pre-refunded municipal bonds |  |  | 53 |  |  |  | 1 |  |  |  | — |  |  |  | 54 |
Corporate bonds |  |  | 30 |  |  |  | — |  |  |  | — |  |  |  | 30 |
Mutual funds, held in rabbi trust |  |  | 8,767 |  |  |  | 365 |  |  |  | — |  |  |  | 9,132 |
|  |  | 8,850 |  |  |  | 366 |  |  |  | — |  |  |  | 9,216 |
|  | $ | 9,351 |  |  | $ | 366 |  |  | $ | — |  |  | $ | 9,717 |

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