Fair Value Measurements and Investments - Investment Income (Detail) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Sep. 30, 2021 |
Sep. 30, 2020 |
Sep. 30, 2019 |
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| Fair Value Disclosures [Abstract] | |||
| Interest and dividend income on cash and investments | $ (16) | $ 80 | $ 247 |
| Realized gains (losses), net on debt securities | 0 | 4 | 1 |
| Equity securities: | |||
| Unrealized gains (losses), net | 721 | 115 | 117 |
| Realized gains (losses), net | 26 | 1 | 18 |
| Investment income | $ 731 | $ 200 | $ 383 |
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- References No definition available.
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- Definition Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount of realized gain (loss) from sale of 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/2009/role/commonPracticeRef
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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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- References No definition available.
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- Definition Amount of operating dividend and interest income, including amortization and accretion of premiums and discounts, on securities. No definition available.
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- Definition Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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