Derivative Financial Instruments (Fair Values of Derivative Instruments) (Details) - USD ($) $ in Millions |
Mar. 31, 2017 |
Sep. 30, 2016 |
|---|---|---|
| Derivative Financial Instruments | ||
| Total derivative assets | $ 26 | $ 46 |
| Other Current Assets [Member] | ||
| Derivative Financial Instruments | ||
| Foreign currency forward exchange contracts | 11 | 11 |
| Other Assets [Member] | ||
| Derivative Financial Instruments | ||
| Interest rate swap assets | 15 | 35 |
| Other Current Liabilities [Member] | ||
| Derivative Financial Instruments | ||
| Foreign currency forward exchange contracts | $ 10 | $ 13 |