Debt (Estimated Fair Value Of Significant Financial Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Estimate of Fair Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term debt	$ 313	$ 264
Long-term debt	5,437	5,444
Reported Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term debt	314	262
Long-term debt	$ 5,510	$ 5,225