Investments - Gains and Losses on Investments within Change in Fair Value (Details) - USD ($) $ in Millions |
12 Months Ended | ||
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Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2024 |
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| Investments, Debt and Equity Securities [Abstract] | |||
| Net loss on equity securities (other) | $ (7) | $ (3) | $ (1) |
| Equity method gain on Other investments | 0 | 0 | 1 |
| Gain or loss on fair value of investments | (7) | (3) | 0 |
| Total net unrealized loss on equity securities | $ (7) | $ (3) | $ (1) |
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- Definition Equity Securities Without Readily Determinable Fair Value, Gain (Loss) No definition available.
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- Definition Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of realized and unrealized gain (loss) on investment. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of income (loss) for proportionate share of equity method investee's income (loss). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- References No definition available.
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