Long-Term Debt and Short-Term Borrowings - Short-Term Borrowings and Current Portion of Long-Term Debt (Details) - USD ($) $ in Millions |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Long-Term Debt | ||
| Total long-term debt | $ 13,198 | $ 11,478 |
| Short-Term Borrowings and Current Portion of Long-Term Debt | ||
| Short-term borrowings and current portion of long-term debt | $ 1,853 | 972 |
| Current portion of long-term debt | ||
| Long-Term Debt | ||
| Interest rate - effective | 0.67% | |
| Total long-term debt | $ 1,102 | 800 |
| Commercial paper | ||
| Long-Term Debt | ||
| Interest rate - effective | 1.50% | |
| Short-Term Borrowings and Current Portion of Long-Term Debt | ||
| Short-term borrowings and current portion of long-term debt | $ 745 | |
| Other borrowings | ||
| Long-Term Debt | ||
| Interest rate - effective | 5.35% | |
| Short-Term Borrowings and Current Portion of Long-Term Debt | ||
| Short-term borrowings and current portion of long-term debt | $ 6 | $ 172 |