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Marketable Securities (Tables) | 3 Months Ended
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Apr. 30, 2022
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 April 30, 2022, January 31, 2022 and April 30, 2021 were as follows:
|  | Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Fair |
|  | Cost |  |  | Gains |  |  | (Losses) |  |  | Value |
As of April 30, 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds |  | $ | 85,474 |  |  | $ | — |  |  | $ | (857 | ) |  | $ | 84,617 |
Municipal and pre-refunded municipal bonds |  |  | 86,134 |  |  |  | — |  |  |  | (633 | ) |  |  | 85,501 |
US Treasury securities |  |  | 9,749 |  |  |  | — |  |  |  | (93 | ) |  |  | 9,656 |
Commercial paper |  |  | 7,789 |  |  |  | — |  |  |  | — |  |  |  | 7,789 |
|  |  | 189,146 |  |  |  | — |  |  |  | (1,583 | ) |  |  | 187,563 |
Long-term Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds |  |  | 117,403 |  |  |  | — |  |  |  | (4,904 | ) |  |  | 112,499 |
Municipal and pre-refunded municipal bonds |  |  | 53,928 |  |  |  | — |  |  |  | (2,081 | ) |  |  | 51,847 |
US Treasury securities |  |  | 3,226 |  |  |  | — |  |  |  | (138 | ) |  |  | 3,088 |
Mutual funds, held in rabbi trust |  |  | 12,393 |  |  |  | — |  |  |  | (956 | ) |  |  | 11,437 |
Federal government agencies |  |  | 350 |  |  |  | — |  |  |  | (12 | ) |  |  | 338 |
Certificates of deposit |  |  | 249 |  |  |  | — |  |  |  | — |  |  |  | 249 |
|  |  | 187,549 |  |  |  | — |  |  |  | (8,091 | ) |  |  | 179,458 |
|  | $ | 376,695 |  |  | $ | — |  |  | $ | (9,674 | ) |  | $ | 367,021 |
As of January 31, 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds |  | $ | 85,062 |  |  | $ | 1 |  |  | $ | (200 | ) |  | $ | 84,863 |
Municipal and pre-refunded municipal bonds |  |  | 128,984 |  |  |  | 1 |  |  |  | (273 | ) |  |  | 128,712 |
US Treasury securities |  |  | 14,999 |  |  |  | — |  |  |  | (38 | ) |  |  | 14,961 |
Commercial paper |  |  | 10,884 |  |  |  | — |  |  |  | — |  |  |  | 10,884 |
|  |  | 239,929 |  |  |  | 2 |  |  |  | (511 | ) |  |  | 239,420 |
Long-term Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds |  |  | 148,830 |  |  |  | — |  |  |  | (2,478 | ) |  |  | 146,352 |
Municipal and pre-refunded municipal bonds |  |  | 60,533 |  |  |  | 1 |  |  |  | (912 | ) |  |  | 59,622 |
US Treasury securities |  |  | 5,222 |  |  |  | — |  |  |  | (46 | ) |  |  | 5,176 |
Mutual funds, held in rabbi trust |  |  | 12,419 |  |  |  | — |  |  |  | (606 | ) |  |  | 11,813 |
Federal government agencies |  |  | 350 |  |  |  | — |  |  |  | (5 | ) |  |  | 345 |
Certificates of deposit |  |  | 249 |  |  |  | — |  |  |  | — |  |  |  | 249 |
|  |  | 227,603 |  |  |  | 1 |  |  |  | (4,047 | ) |  |  | 223,557 |
|  | $ | 467,532 |  |  | $ | 3 |  |  | $ | (4,558 | ) |  | $ | 462,977 |
|  | Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Fair |
|  | Cost |  |  | Gains |  |  | (Losses) |  |  | Value |
As of April 30, 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Short-term Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds |  | $ | 48,500 |  |  | $ | 1 |  |  | $ | (49 | ) |  | $ | 48,452 |
Municipal and pre-refunded municipal bonds |  |  | 106,266 |  |  |  | 5 |  |  |  | (84 | ) |  |  | 106,187 |
Commercial paper |  |  | 9,791 |  |  |  | — |  |  |  | — |  |  |  | 9,791 |
|  |  | 164,557 |  |  |  | 6 |  |  |  | (133 | ) |  |  | 164,430 |
Long-term Investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds |  |  | 48,850 |  |  |  | 2 |  |  |  | (111 | ) |  |  | 48,741 |
Municipal and pre-refunded municipal bonds |  |  | 40,085 |  |  |  | 17 |  |  |  | (48 | ) |  |  | 40,054 |
Mutual funds, held in rabbi trust |  |  | 11,448 |  |  |  | 437 |  |  |  | — |  |  |  | 11,885 |
|  |  | 100,383 |  |  |  | 456 |  |  |  | (159 | ) |  |  | 100,680 |
|  | $ | 264,940 |  |  | $ | 462 |  |  | $ | (292 | ) |  | $ | 265,110 |

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