Derivatives and Financial Instruments (Summary of Gains/(Losses) From Commodity Derivatives) (Details) - Commodity derivatives - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of gains (losses) from commodity derivatives
Net gain (loss) from commodity derivative activity	$ (278)	$ 113	$ (238)
Sales and other operating revenues
Summary of gains (losses) from commodity derivatives
Net gain (loss) from commodity derivative activity	(150)	192	(247)
Other income
Summary of gains (losses) from commodity derivatives
Net gain (loss) from commodity derivative activity	33	(15)	27
Purchased crude oil and products
Summary of gains (losses) from commodity derivatives
Net gain (loss) from commodity derivative activity	$ (161)	$ (64)	$ (18)