| Summary of Financial Assets Measured at Fair Value on Recurring Basis |
The following table sets forth our financial assets as of December 31, 2020 and 2019 that are measured at fair value on a recurring basis during the period:
|
|
December 31, 2020 |
|
|
|
Cost or
Amortized Cost |
|
|
Gross
Unrealized
Gains |
|
|
Gross
Unrealized
Losses |
|
|
Total Estimated
Fair Value |
|
|
|
(in thousands) |
|
|
Cash |
$ |
464,006 |
|
|
$ |
— |
|
|
$ |
— |
|
|
$ |
464,006 |
|
|
Level 1 securities: |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
U.S. government securities |
|
1,272,125 |
|
|
|
122 |
|
|
|
(21 |
) |
|
|
1,272,226 |
|
|
U.S. government agency securities |
|
245,055 |
|
|
|
8 |
|
|
|
(24 |
) |
|
|
245,039 |
|
|
Level 2 securities: |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Corporate debt securities |
|
81,158 |
|
|
|
1 |
|
|
|
(18 |
) |
|
|
81,141 |
|
|
Commercial paper |
|
425,861 |
|
|
|
— |
|
|
|
— |
|
|
|
425,861 |
|
|
Certificates of deposit |
|
49,267 |
|
|
|
— |
|
|
|
— |
|
|
|
49,267 |
|
|
Total |
$ |
2,537,472 |
|
|
$ |
131 |
|
|
$ |
(63 |
) |
|
$ |
2,537,540 |
|
|
|
December 31, 2019 |
|
|
|
Cost or
Amortized Cost |
|
|
Gross
Unrealized
Gains |
|
|
Gross
Unrealized
Losses |
|
|
Total Estimated
Fair Value |
|
|
|
(in thousands) |
|
|
Cash |
$ |
416,099 |
|
|
$ |
— |
|
|
$ |
— |
|
|
$ |
416,099 |
|
|
Level 1 securities: |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
U.S. government securities |
|
1,305,145 |
|
|
|
604 |
|
|
|
(49 |
) |
|
|
1,305,700 |
|
|
U.S. government agency securities |
|
269,278 |
|
|
|
48 |
|
|
|
(32 |
) |
|
|
269,294 |
|
|
Level 2 securities: |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Corporate debt securities |
|
28,420 |
|
|
|
13 |
|
|
|
(4 |
) |
|
|
28,429 |
|
|
Commercial paper |
|
84,498 |
|
|
|
— |
|
|
|
— |
|
|
|
84,498 |
|
|
Certificates of deposit |
|
8,785 |
|
|
|
— |
|
|
|
— |
|
|
|
8,785 |
|
|
Total |
$ |
2,112,225 |
|
|
$ |
665 |
|
|
$ |
(85 |
) |
|
$ |
2,112,805 |
|
|