| Schedule of available-for-sale securities |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | December 31, 2023 | | December 31, 2022 | | | | Amortized
Cost | | Gross
Unrealized
Gain | | Gross
Unrealized
(Loss) | | Estimated Fair
Value | | Amortized
Cost | | Gross
Unrealized
Gain | | Gross
Unrealized
(Loss) | | Estimated Fair
Value | | | | | (in thousands) | | Cash, cash equivalents and restricted cash (2) | | | 642,095 | | | — | | | — | | | 642,095 | | | 466,091 | | | — | | | — | | | 466,091 | | U.S. Treasury securities (1) | | | 201,522 | | | 14 | | | (1,118) | | | 200,418 | | | 358,385 | | | — | | | (12,328) | | | 346,057 | | Corporate bonds and notes (1) | | | — | | | — | | | — | | | — | | | 24,045 | | | — | | | (516) | | | 23,529 | | Municipal securities (1) | | | 38,091 | | | — | | | (1,627) | | | 36,464 | | | 65,973 | | | 1 | | | (3,259) | | | 62,715 | | Total | | $ | 881,708 | | $ | 14 | | $ | (2,745) | | $ | 878,977 | | $ | 914,494 | | $ | 1 | | $ | (16,103) | | $ | 898,392 | | | | | | | | | | | | | | | | | | | | | | | | | | | | Classified as: | | | | | | | | | | | | | | | | | | | | | | | | | | Cash, cash equivalents and restricted cash (2) | | | | | | | | | | | $ | 642,095 | | | | | | | | | | | $ | 466,091 | | Short-term investments | | | | | | | | | | | | 236,882 | | | | | | | | | | | | 432,301 | | Total | | | | | | | | | | | $ | 878,977 | | | | | | | | | | | $ | 898,392 | |
| (1) Per the Company’s investment policy, all debt securities are classified as short-term investments irrespective of holding period. |
| (2) | Cash equivalents includes liquid demand deposits, money market funds, and other liquid investments having an original maturity of less than three months. |
|
| Summarized portfolio of available-for-sale securities by contractual maturity |
| | | | | | | | | | December 31, 2023 | | | | Amortized
Cost | | Fair
Value | | | | | (in thousands) | | Less than or equal to one year | | $ | 216,548 | | $ | 215,095 | | Greater than one year but less than five years | | | 23,065 | | | 21,787 | | Total | | $ | 239,613 | | $ | 236,882 | |
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