Fair Value Measurements and Investments - Schedule of Continuous Unrealized Losses for Less than 12 Months and More than 12 Months (Details) - USD ($) $ in Millions |
Sep. 30, 2024 |
Sep. 30, 2023 |
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| Debt Securities, Available-for-sale [Line Items] | ||
| Less Than 12 Months, Fair Value | $ 0 | $ 1,772 |
| Less Than 12 Months, Gross Unrealized Losses | 0 | (14) |
| 12 Months or Greater, Fair Value | 1,183 | 2,178 |
| 12 Months or Greater, Gross Unrealized Losses | (5) | (68) |
| U.S. government-sponsored debt securities | ||
| Debt Securities, Available-for-sale [Line Items] | ||
| Less Than 12 Months, Fair Value | 0 | 412 |
| Less Than 12 Months, Gross Unrealized Losses | 0 | (2) |
| 12 Months or Greater, Fair Value | 164 | 50 |
| 12 Months or Greater, Gross Unrealized Losses | 0 | 0 |
| U.S. Treasury securities | ||
| Debt Securities, Available-for-sale [Line Items] | ||
| Less Than 12 Months, Fair Value | 0 | 1,360 |
| Less Than 12 Months, Gross Unrealized Losses | 0 | (12) |
| 12 Months or Greater, Fair Value | 1,019 | 2,128 |
| 12 Months or Greater, Gross Unrealized Losses | $ (5) | $ (68) |
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset. Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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