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v3.23.3

Note 5 - Financial Instruments Measured at Fair Value (Tables) | 9 Months Ended
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Sep. 30, 2023
Notes Tables |
Unrealized Gain (Loss) on Investments [Table Text Block] |
|  | September 30, 2023 |
|  |  |  |  |  | Gross |  |  | Gross |  |  | Estimated |
|  | Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Fair |
|  | Cost |  |  | Gains |  |  | Losses (1) |  |  | Value |
Corporate debt securities (2) |  | $ | 40,601 |  |  | $ | 2 |  |  | $ | 75 |  |  | $ | 40,528 |
Bank certificates of deposit |  |  | 22,640 |  |  |  | 6 |  |  |  | 7 |  |  |  | 22,639 |
U.S. treasury securities |  |  | 21,918 |  |  |  | - |  |  |  | 251 |  |  |  | 21,667 |
Asset-backed securities |  |  | 8,652 |  |  |  | - |  |  |  | 31 |  |  |  | 8,621 |
Foreign government security |  |  | 725 |  |  |  | - |  |  |  | - |  |  |  | 725 |
|  | $ | 94,536 |  |  | $ | 8 |  |  | $ | 364 |  |  | $ | 94,180 |
|  | December 31, 2022 |
|  |  |  |  |  | Gross |  |  | Gross |  |  | Estimated |
|  | Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Fair |
|  | Cost |  |  | Gains |  |  | Losses (1) |  |  | Value |
Corporate debt securities (2) |  | $ | 59,283 |  |  | $ | 30 |  |  | $ | 240 |  |  | $ | 59,073 |
Bank certificates of deposit |  |  | 36,500 |  |  |  | 20 |  |  |  | 41 |  |  |  | 36,479 |
U.S. treasury securities |  |  | 34,614 |  |  |  | 1 |  |  |  | 418 |  |  |  | 34,197 |
Asset-backed securities |  |  | 12,727 |  |  |  | 10 |  |  |  | 79 |  |  |  | 12,658 |
Foreign government security |  |  | 828 |  |  |  | - |  |  |  | - |  |  |  | 828 |
|  | $ | 143,952 |  |  | $ | 61 |  |  | $ | 778 |  |  | $ | 143,235 |
Investments Classified by Contractual Maturity Date [Table Text Block] |
|  | September 30, 2023 |  |  | December 31, 2022 |
|  | Amortized |  |  | Estimated |  |  | Amortized |  |  | Estimated |
|  | Cost |  |  | Fair Value |  |  | Cost |  |  | Fair Value |
Due in one year or less |  | $ | 70,275 |  |  | $ | 70,012 |  |  | $ | 112,956 |  |  | $ | 112,683 |
Due after one year through five years |  |  | 23,536 |  |  |  | 23,443 |  |  |  | 30,996 |  |  |  | 30,552 |
Due after five years through ten years |  |  | 725 |  |  |  | 725 |  |  |  | - |  |  |  | - |
|  | $ | 94,536 |  |  | $ | 94,180 |  |  | $ | 143,952 |  |  | $ | 143,235 |
Fair Value, Assets Measured on Recurring Basis [Table Text Block] |
|  | Fair value measurements at September 30, 2023 using: |
|  |  |  |  |  |  |  |  |  |  |  |  |  | Total estimated |
|  | Level 1 |  |  | Level 2 |  |  | Level 3 |  |  | fair value |
Cash |  | $ | 243,956 |  |  | $ | - |  |  | $ | - |  |  | $ | 243,956 |
U.S. treasury securities |  |  | - |  |  |  | 21,667 |  |  |  | - |  |  |  | 21,667 |
Corporate debt securities |  |  | - |  |  |  | 41,523 |  |  |  | - |  |  |  | 41,523 |
Asset-backed securities |  |  | - |  |  |  | 8,621 |  |  |  | - |  |  |  | 8,621 |
Money market funds |  |  | - |  |  |  | 48,435 |  |  |  | - |  |  |  | 48,435 |
Bank certificates of deposit |  |  | - |  |  |  | 22,639 |  |  |  | - |  |  |  | 22,639 |
Foreign government security |  |  | - |  |  |  | 725 |  |  |  | - |  |  |  | 725 |
|  | $ | 243,956 |  |  | $ | 143,610 |  |  | $ | - |  |  | $ | 387,566 |
|  | Fair value measurements at December 31, 2022 using: |
|  |  |  |  |  |  |  |  |  |  |  |  |  | Total estimated |
|  | Level 1 |  |  | Level 2 |  |  | Level 3 |  |  | fair value |
Cash |  | $ | 190,371 |  |  | $ | - |  |  | $ | - |  |  | $ | 190,371 |
Corporate debt securities |  |  | - |  |  |  | 69,753 |  |  |  | - |  |  |  | 69,753 |
Money market funds |  |  | - |  |  |  | 40,290 |  |  |  | - |  |  |  | 40,290 |
Bank certificates of deposit |  |  | - |  |  |  | 37,480 |  |  |  | - |  |  |  | 37,480 |
U.S. treasury securities |  |  | - |  |  |  | 34,196 |  |  |  | - |  |  |  | 34,196 |
Asset-backed securities |  |  | - |  |  |  | 12,658 |  |  |  | - |  |  |  | 12,658 |
Foreign government security |  |  | - |  |  |  | 828 |  |  |  | - |  |  |  | 828 |
|  | $ | 190,371 |  |  | $ | 195,205 |  |  | $ | - |  |  | $ | 385,576 |

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