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Other Income (Expense), Net Other Income (Expense), Net (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2016
Other Income (Expense), Net |  |  |
Interest income | $ 23 | $ 23 | $ 24
External services | 14 | 14 | 12
Gains (losses) on investments | 6 | 9 | 7
Miscellaneous |  | (10) | 0
Miscellaneous | 7 |  |
Total other income (expense), net | $ 50 | $ 56 | $ 43

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