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Marketable Securities (Tables) | 9 Months Ended
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Oct. 31, 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 October 31, 2022, January 31, 2022 and October 31, 2021 were as follows:
|  | Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Fair |
|  | Cost |  |  | Gains |  |  | (Losses) |  |  | Value |
As of October 31, 2022 |  |  |  |  |  |  |  |  |  |  |  |
Short-term Investments: |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds |  | $ | 85,788 |  |  | $ | — |  |  | $ | (1,626 | ) |  | $ | 84,162 |
Municipal and pre-refunded municipal bonds |  |  | 58,417 |  |  |  | — |  |  |  | (910 | ) |  |  | 57,507 |
US Treasury securities |  |  | 4,750 |  |  |  | — |  |  |  | (55 | ) |  |  | 4,695 |
|  |  | 148,955 |  |  |  | — |  |  |  | (2,591 | ) |  |  | 146,364 |
Long-term Investments: |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds |  |  | 61,707 |  |  |  | — |  |  |  | (4,472 | ) |  |  | 57,235 |
Municipal and pre-refunded municipal bonds |  |  | 28,803 |  |  |  | — |  |  |  | (1,801 | ) |  |  | 27,002 |
Mutual funds, held in rabbi trust |  |  | 12,546 |  |  |  | — |  |  |  | (1,786 | ) |  |  | 10,760 |
Certificates of deposit |  |  | 249 |  |  |  | — |  |  |  | — |  |  |  | 249 |
|  |  | 103,305 |  |  |  | — |  |  |  | (8,059 | ) |  |  | 95,246 |
|  | $ | 252,260 |  |  | $ | — |  |  | $ | (10,650 | ) |  | $ | 241,610 |
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 |
Mutual funds, held in rabbi trust |  |  | 12,419 |  |  |  | — |  |  |  | (606 | ) |  |  | 11,813 |
US Treasury securities |  |  | 5,222 |  |  |  | — |  |  |  | (46 | ) |  |  | 5,176 |
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 October 31, 2021 |  |  |  |  |  |  |  |  |  |  |  |
Short-term Investments: |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds |  | $ | 53,744 |  |  | $ | 3 |  |  | $ | (71 | ) |  | $ | 53,676 |
Municipal and pre-refunded municipal bonds |  |  | 114,818 |  |  |  | 9 |  |  |  | (73 | ) |  |  | 114,754 |
US Treasury securities |  |  | 16,849 |  |  |  | — |  |  |  | (3 | ) |  |  | 16,846 |
Commercial paper |  |  | 3,099 |  |  |  | — |  |  |  | — |  |  |  | 3,099 |
|  |  | 188,510 |  |  |  | 12 |  |  |  | (147 | ) |  |  | 188,375 |
Long-term Investments: |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds |  |  | 174,884 |  |  |  | 1 |  |  |  | (1,125 | ) |  |  | 173,760 |
Municipal and pre-refunded municipal bonds |  |  | 78,955 |  |  |  | 8 |  |  |  | (362 | ) |  |  | 78,601 |
Mutual funds, held in rabbi trust |  |  | 11,540 |  |  |  | 542 |  |  |  | (1 | ) |  |  | 12,081 |
US Treasury securities |  |  | 4,748 |  |  |  | — |  |  |  | (7 | ) |  |  | 4,741 |
Federal government agencies |  |  | 350 |  |  |  | — |  |  |  | (2 | ) |  |  | 348 |
Certificates of deposit |  |  | 249 |  |  |  | — |  |  |  | — |  |  |  | 249 |
|  |  | 270,726 |  |  |  | 551 |  |  |  | (1,497 | ) |  |  | 269,780 |
|  | $ | 459,236 |  |  | $ | 563 |  |  | $ | (1,644 | ) |  | $ | 458,155 |

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