| Fair Value of Financial Instruments |
Fair Value of Financial Instruments The fair values of the financial instruments we measure at fair value on a recurring basis are as follows (in thousands): | | | | | | | | | | | | | | | | | | | | | | | | | March 31, 2024 | | Level 1 | | Level 2 | | Level 3 | | Total | | Cash equivalents: | | | | | | | | | Money market funds | $ | 1,332,610 | | | $ | — | | | $ | — | | | $ | 1,332,610 | | | Commercial paper | — | | | 116,808 | | | — | | | 116,808 | | | | | | | | | | | U.S. treasury securities | 21,809 | | | — | | | — | | | 21,809 | | | | | | | | | | | | | | | | | | | Marketable securities: | | | | | | | | | Corporate bonds | — | | | 457,432 | | | — | | | 457,432 | | | Commercial paper | — | | | 257,031 | | | — | | | 257,031 | | | U.S. treasury securities | 250,212 | | | — | | | — | | | 250,212 | | | Certificates of deposit | — | | | 137,278 | | | — | | | 137,278 | | | | | | | | | | | Non-U.S. government and supranational bonds | — | | | 9,013 | | | — | | | 9,013 | | | U.S. agency bonds | — | | | 33,294 | | | — | | | 33,294 | | | | | | | | | | | Prepaid expenses and other current assets: | | | | | | | | | Certificates of deposit | — | | | 1,695 | | | — | | | 1,695 | | | Restricted cash: | | | | | | | | | Certificates of deposit | — | | | 4,054 | | | — | | | 4,054 | | | | | | | | | | | | | | | | | | | | | | | | | |
| | | | | | | | | | | | | | | | | | | | | | | | | December 31, 2023 | | Level 1 | | Level 2 | | Level 3 | | Total | | Cash equivalents: | | | | | | | | | Money market funds | $ | 1,032,675 | | | $ | — | | | $ | — | | | $ | 1,032,675 | | | Commercial paper | — | | | 106,268 | | | — | | | 106,268 | | | Certificates of deposit | — | | | 1,551 | | | — | | | 1,551 | | | | | | | | | | | Corporate bonds | — | | | 859 | | | — | | | 859 | | | | | | | | | | | Marketable securities: | | | | | | | | | Corporate bonds | — | | | 427,957 | | | — | | | 427,957 | | | Commercial paper | — | | | 201,145 | | | — | | | 201,145 | | | U.S. treasury securities | 336,356 | | | — | | | — | | | 336,356 | | | Certificates of deposit | — | | | 132,457 | | | — | | | 132,457 | | | | | | | | | | | Non-U.S. government and supranational bonds | — | | | 8,983 | | | — | | | 8,983 | | | U.S. agency bonds | — | | | 42,250 | | | — | | | 42,250 | | | | | | | | | | | Prepaid expenses and other current assets: | | | | | | | | | Certificates of deposit | — | | | 2,542 | | | — | | | 2,542 | | | Restricted cash: | | | | | | | | | Certificates of deposit | — | | | 4,054 | | | — | | | 4,054 | | | | | | | | | | | | | | | | | |
We classify our marketable securities within Level 1 or Level 2 because we determine their fair values using quoted market prices or alternative pricing sources and models utilizing market observable inputs. Gross unrealized gains and losses on our marketable securities were not material in the aggregate as of March 31, 2024 and December 31, 2023. We evaluated all available evidence and did not recognize any allowance for credit losses for our marketable securities as of March 31, 2024 and December 31, 2023. The fair value of our marketable securities by contractual maturity is as follows (in thousands): | | | | | | | March 31, 2024 | | Due in one year or less | $ | 848,270 | | | Due after one to five years | 295,990 | | | Total | $ | 1,144,260 | |
Net realized gains and losses from sales of available-for-sale securities were not material for any period presented.
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