| Schedule of Fair Value of Financial Assets by Level |
The following tables summarize the fair value of these financial assets by significant investment category and their levels within the fair value hierarchy (in thousands): | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | March 31, 2024 | | December 31, 2023 | | | Level I | | Level II | | Level III | | Total | | Level I | | Level II | | Level III | | Total | | Financial Assets: | | | | | | | | | | | | | | | | | | Cash Equivalents: | | | | | | | | | | | | | | | | | | Money market funds | | $ | 1,035,025 | | | $ | — | | | $ | — | | | $ | 1,035,025 | | | $ | 1,015,705 | | | $ | — | | | $ | — | | | $ | 1,015,705 | | | Commercial paper | | — | | | 8,980 | | | — | | | 8,980 | | | — | | | 1,999 | | | — | | | 1,999 | | | Corporate bonds | | — | | | 1,988 | | | — | | | 1,988 | | | — | | | — | | | — | | | — | | | | | | | | | | | | | | | | | | | | U.S. government notes | | 310,801 | | | — | | | — | | | 310,801 | | | — | | | — | | | — | | | — | | | | | | | | | | | | | | | | | | | | | 1,345,826 | | | 10,968 | | | — | | | 1,356,794 | | | 1,015,705 | | | 1,999 | | | — | | | 1,017,704 | | | Marketable Securities: | | | | | | | | | | | | | | | | | | Commercial paper | | — | | | 15,640 | | | — | | | 15,640 | | | — | | | — | | | — | | | — | | Certificates of deposits(1) | | — | | | — | | | — | | | — | | | — | | | 5,000 | | | — | | | 5,000 | | | U.S. government notes | | 1,236,709 | | | — | | | — | | | 1,236,709 | | | 1,044,859 | | | — | | | — | | | 1,044,859 | | | Corporate bonds | | — | | | 1,554,965 | | | — | | | 1,554,965 | | | — | | | 1,362,124 | | | — | | | 1,362,124 | | | Agency securities | | — | | | 550,283 | | | — | | | 550,283 | | | — | | | 657,379 | | | — | | | 657,379 | | | | | | | | | | | | | | | | | | | | | 1,236,709 | | | 2,120,888 | | | — | | | 3,357,597 | | | 1,044,859 | | | 2,024,503 | | | — | | | 3,069,362 | | | Other Assets: | | | | | | | | | | | | | | | | | | Money market funds - restricted | | 860 | | | — | | | — | | | 860 | | | 858 | | | — | | | — | | | 858 | | | Total Financial Assets | | $ | 2,583,395 | | | $ | 2,131,856 | | | $ | — | | | $ | 4,715,251 | | | $ | 2,061,422 | | | $ | 2,026,502 | | | $ | — | | | $ | 4,087,924 | |
______________________________________ (1) As of December 31, 2023, all of our certificates of deposits were domestic deposits. The following table summarizes the amortized cost, unrealized gains and losses, and fair value of our debt securities measured at fair value on a recurring basis (in thousands): | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | March 31, 2024 | | December 31, 2023 | | | Amortized Cost | | Unrealized Gains | | Unrealized Losses | | Fair Value | | Amortized Cost | | Unrealized Gains | | Unrealized Losses | | Fair Value | | Commercial paper | | $ | 15,640 | | | $ | — | | | $ | — | | | $ | 15,640 | | | $ | — | | | $ | — | | | $ | — | | | $ | — | | | U.S. government | | 1,238,929 | | | 468 | | | (2,688) | | | 1,236,709 | | | 1,043,445 | | | 2,874 | | | (1,460) | | | 1,044,859 | | | Corporate bonds | | 1,558,489 | | | 618 | | | (4,142) | | | 1,554,965 | | | 1,361,132 | | | 2,810 | | | (1,818) | | | 1,362,124 | | | Agency securities | | 551,315 | | | 145 | | | (1,177) | | | 550,283 | | | 657,118 | | | 1,143 | | | (882) | | | 657,379 | | | | | | | | | | | | | | | | | | | | Total | | $ | 3,364,373 | | | $ | 1,231 | | | $ | (8,007) | | | $ | 3,357,597 | | | $ | 3,061,695 | | | $ | 6,827 | | | $ | (4,160) | | | $ | 3,064,362 | |
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| Schedule of Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value |
The following table is an analysis of our marketable debt securities in unrealized loss positions (in thousands): | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | March 31, 2024 | | | Unrealized Losses within 12 months | | Unrealized Losses 12 months or greater | | Total | | | Fair Value | | Unrealized Losses | | Fair Value | | Unrealized Losses | | Fair Value | | Unrealized Losses | | U.S. government notes | | $ | 730,912 | | | $ | (2,688) | | | $ | — | | | $ | — | | | $ | 730,912 | | | $ | (2,688) | | | Corporate bonds | | 1,330,835 | | | (3,944) | | | 68,345 | | | (198) | | | 1,399,180 | | | (4,142) | | | Agency securities | | 424,306 | | | (1,124) | | | 9,979 | | | (53) | | | 434,285 | | | (1,177) | | | Total | | $ | 2,486,053 | | | $ | (7,756) | | | $ | 78,324 | | | $ | (251) | | | $ | 2,564,377 | | | $ | (8,007) | |
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