Debt (Estimated Fair Value Of Significant Financial Instruments) (Details) - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
---|---|---|
Carrying Amount | ||
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
Short-term debt | $ 517 | $ 1,215 |
Long-term debt | 10,796 | 10,741 |
Fair Value | ||
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
Short-term debt | 523 | 1,229 |
Long-term debt | $ 12,858 | $ 11,953 |