Derivative Financial Instruments (Schedule Of Derivative Financial Instruments Included In The Consolidated Comprehensive Statements Of Earnings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Net gains (losses) recognized in consolidated comprehensive statements of earnings	$ 134	$ (386)	$ 738
Commodity Derivatives [Member] | Upstream Revenues [Member]
Derivative [Line Items]
Net gains (losses) recognized in consolidated comprehensive statements of earnings	157	(201)	503
Commodity Derivatives [Member] | Marketing And Midstream Revenues [Member]
Derivative [Line Items]
Net gains (losses) recognized in consolidated comprehensive statements of earnings	(1)	(13)	9
Interest Rate Derivatives [Member] | Other Expenses [Member]
Derivative [Line Items]
Net gains (losses) recognized in consolidated comprehensive statements of earnings	$ (22)	(19)	(20)
Foreign Currency Derivatives [Member] | Other Expenses [Member]
Derivative [Line Items]
Net gains (losses) recognized in consolidated comprehensive statements of earnings		$ (153)	$ 246