Long-Term Debt and Short-Term Borrowings - Long-Term Debt Maturities (Details) - USD ($) $ in Millions |
3 Months Ended | |||
|---|---|---|---|---|
Dec. 31, 2017 |
Oct. 31, 2017 |
Jun. 30, 2017 |
Sep. 30, 2016 |
|
| Debt instrument | ||||
| Debt repurchases | $ 305 | |||
| Loss on early debt extinguishment | $ 96 | |||
| Fixed rate medium term notes repaid June 2017 | ||||
| Debt instrument | ||||
| Principal amount | $ 650 | |||
| Notes Due 2028 | ||||
| Debt instrument | ||||
| Debt repurchases | 110 | |||
| Principal amount | $ 330 | |||
| Interest rate, stated percentage (as a percent) | 6.375% | |||
| Notes Due 2037 | ||||
| Debt instrument | ||||
| Debt repurchases | $ 195 | |||
| Principal amount | $ 750 | |||
| Interest rate, stated percentage (as a percent) | 5.70% | |||
| Fixed rate medium term notes repaid 2016 | ||||
| Debt instrument | ||||
| Principal amount | $ 1,000 |