Debt (Debt Textuals) (Details) - USD ($) $ in Millions |
Mar. 31, 2017 |
Dec. 31, 2016 |
Sep. 30, 2015 |
|---|---|---|---|
| Line of Credit Facility [Line Items] | |||
| Debt and Capital Lease Obligations | $ 11,952 | $ 12,179 | |
| Debt Instruments [Abstract] | |||
| Debt Instrument, Interest Rate, Effective Percentage | 5.40% | 5.50% | |
| Revolving Credit Facility [Member] | |||
| Line of Credit Facility [Line Items] | |||
| Debt and Capital Lease Obligations | $ 25 | 0 | |
| Notes Payable, Other Payables [Member] | |||
| Line of Credit Facility [Line Items] | |||
| Debt and Capital Lease Obligations | $ 1,561 | $ 1,597 |