Financial Instruments And Derivatives (Narrative) (Details) bbl in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018 bbl	Dec. 31, 2017 USD ($)
Financial Instruments And Derivatives [Line Items]
Estimated fair value of total long-term debt, excluding capitalized lease obligations		$ 23,700
Recorded book values of total long-term debt, excluding capitalized lease obligations		23,100
Gross assets		25
Gross liabilities		(63)
Collateral receivable		$ 94
Crude Oil [Member] | Short [Member]
Financial Instruments And Derivatives [Line Items]
Net notional long / short position of derivative instruments bbl | bbl	19
Products [Member] | Short [Member]
Financial Instruments And Derivatives [Line Items]
Net notional long / short position of derivative instruments bbl | bbl	9