Fair Value Measurements and Investments - Schedule of Non-Marketable Equity Securities (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2017 |
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| Schedule of Equity Securities [Roll Forward] | |||
| Carrying amount, beginning of period | $ 137 | ||
| Net additions (reductions) | 475 | ||
| Upward adjustments | 110 | ||
| Downward adjustments | (4) | ||
| Carrying amount, end of period | 718 | $ 137 | |
| Impairment charges of non-marketable equity securities | $ 0 | $ 0 | $ 0 |
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- Definition Amount 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/2003/role/disclosureRef
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- Definition Amount of loss from downward price adjustment on investment in equity security without readily determinable fair value. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of gain from upward price adjustment on investment in equity security without readily determinable fair value. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Equity Securities without Readily Determinable Fair Value, Additions (Reductions), Annual Amount No definition available.
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- Definition Schedule of Equity Securities [Roll Forward] No definition available.
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