| Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis |
Our assets and liabilities that were measured at fair value on a recurring basis were as follows (in millions): | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | March 31, 2024 | | December 31, 2023 | | | Fair Value | | Level I | | Level II | | Level III | | Fair Value | | Level I | | Level II | | Level III | | Money market funds | $ | 368 | | | $ | 368 | | | $ | — | | | $ | — | | | $ | 109 | | | $ | 109 | | | $ | — | | | $ | — | | | U.S. government securities | 4,122 | | | — | | | 4,122 | | | — | | | 5,136 | | | — | | | 5,136 | | | — | | | Corporate debt securities | 420 | | | — | | | 420 | | | — | | | 480 | | | — | | | 480 | | | — | | | Certificates of deposit and time deposits | 8,155 | | | — | | | 8,155 | | | — | | | 6,996 | | | — | | | 6,996 | | | — | | | Commercial paper | 2,411 | | | — | | | 2,411 | | | — | | | 470 | | | — | | | 470 | | | — | | | Total | $ | 15,476 | | | $ | 368 | | | $ | 15,108 | | | $ | — | | | $ | 13,191 | | | $ | 109 | | | $ | 13,082 | | | $ | — | |
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| Unrealized Gain (Loss) on Investments |
Our cash, cash equivalents and investments classified by security type as of March 31, 2024 and December 31, 2023 consisted of the following (in millions): | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | March 31, 2024 | | | Adjusted Cost | | Gross Unrealized Gains | | Gross Unrealized Losses | | Fair Value | | Cash and Cash Equivalents | | Short-Term Investments | | Cash | $ | 11,387 | | | $ | — | | | $ | — | | | $ | 11,387 | | | $ | 11,387 | | | $ | — | | | Money market funds | 368 | | | — | | | — | | | 368 | | | 368 | | | — | | | U.S. government securities | 4,124 | | | — | | | (2) | | | 4,122 | | | — | | | 4,122 | | | Corporate debt securities | 423 | | | 1 | | | (4) | | | 420 | | | — | | | 420 | | | Certificates of deposit and time deposits | 8,155 | | | — | | | — | | | 8,155 | | | — | | | 8,155 | | | Commercial paper | 2,414 | | | — | | | (3) | | | 2,411 | | | 50 | | | 2,361 | | | Total cash, cash equivalents and short-term investments | $ | 26,871 | | | $ | 1 | | | $ | (9) | | | $ | 26,863 | | | $ | 11,805 | | | $ | 15,058 | |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | December 31, 2023 | | | Adjusted Cost | | Gross Unrealized Gains | | Gross Unrealized Losses | | Fair Value | | Cash and Cash Equivalents | | Short-Term Investments | | Cash | $ | 15,903 | | | $ | — | | | $ | — | | | $ | 15,903 | | | $ | 15,903 | | | $ | — | | | Money market funds | 109 | | | — | | | — | | | 109 | | | 109 | | | — | | | U.S. government securities | 5,136 | | | 1 | | | (1) | | | 5,136 | | | 277 | | | 4,859 | | | Corporate debt securities | 485 | | | 1 | | | (6) | | | 480 | | | — | | | 480 | | | Certificates of deposit and time deposits | 6,995 | | | 1 | | | — | | | 6,996 | | | — | | | 6,996 | | | Commercial paper | 470 | | | — | | | — | | | 470 | | | 109 | | | 361 | | | Total cash, cash equivalents and short-term investments | $ | 29,098 | | | $ | 3 | | | $ | (7) | | | $ | 29,094 | | | $ | 16,398 | | | $ | 12,696 | |
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