Financial and Derivative Instruments Financial and Derivative Instruments - Effect of Derivatives Not Designated On Hedging Instruments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ 105	$ (116)	$ (300)
Commodity | Sales and other operating revenues
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	135	(105)	(269)
Commodity | Purchased crude oil and products
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	(33)	(9)	(31)
Commodity | Other income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ 3	$ (2)	$ 0