Sales and Other Operating Revenues (Disaggregated) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	$ 27,847	$ 28,980	$ 50,950	$ 52,575
United States
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	21,867	22,902	39,442	41,413
United Kingdom
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	2,512	2,289	4,943	4,538
Germany
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	1,092	1,108	2,049	2,039
Other foreign countries
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	2,376	2,681	4,516	4,585
Refined petroleum products
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	22,922	23,011	41,715	41,791
Crude oil resales
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	3,613	4,381	6,651	7,569
Natural gas liquids (NGLs)
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	1,179	1,548	2,483	2,969
Services and other
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	$ 133	$ 40	$ 101	$ 246