Note 5 - Financial Instruments Measured at Fair Value (Tables)
|
9 Months Ended |
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 |
|
|