Debt (Narrative) (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Debt Instrument [Line Items] | ||
| Debt Instrument Weighted Average Interest Rate | 4.40% | 4.40% |
| Debt Instrument - principal/face amount | $ 17,235 | |
| Debt Issued in Foreign Markets [Member] | ||
| Debt Instrument [Line Items] | ||
| Debt Instrument - principal/face amount | $ 42,485 | $ 41,356 |
| Annual Put Reset Securities [Member] | ||
| Debt Instrument [Line Items] | ||
| Debt instruments - maturity date | Apr. 30, 2021 | |
| Debt Instrument - principal/face amount | $ 1,000 | |
| Zero Coupon [Member] | ||
| Debt Instrument [Line Items] | ||
| Debt instruments - maturity date | May 31, 2022 | |
| Debt Instrument - principal/face amount | $ 500 | |
| Debt instrument - redemption amount | $ 592 |