4. Investments
As of December 31, 2019 and 2018, the fair value of available-for-sale investments by type of security was as follows:
|
|
December 31, 2019 |
|
|
|
Amortized
Cost |
|
|
Gross
Unrealized
Gain |
|
|
Gross
Unrealized
Loss |
|
|
Fair
Value |
|
Investments: |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Corporate notes |
|
$ |
5,489 |
|
|
$ |
2 |
|
|
$ |
— |
|
|
$ |
5,491 |
|
Commercial paper |
|
|
7,470 |
|
|
|
6 |
|
|
|
— |
|
|
|
7,476 |
|
|
|
$ |
12,959 |
|
|
$ |
8 |
|
|
$ |
— |
|
|
$ |
12,967 |
|
|
|
December 31, 2018 |
|
|
|
Amortized
Cost |
|
|
Gross
Unrealized
Gain |
|
|
Gross
Unrealized
Loss |
|
|
Fair
Value |
|
Investments: |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Corporate notes |
|
$ |
3,647 |
|
|
$ |
— |
|
|
$ |
(3 |
) |
|
$ |
3,644 |
|
Commercial paper |
|
|
6,418 |
|
|
|
— |
|
|
|
(2 |
) |
|
|
6,416 |
|
|
|
$ |
10,065 |
|
|
$ |
— |
|
|
$ |
(5 |
) |
|
$ |
10,060 |
|
|