Sales and Other Operating Revenues (Disaggregated) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	$ 20,878	$ 23,103
United States
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	15,710	17,575
United Kingdom
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	2,309	2,431
Germany
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	858	957
Other foreign countries
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	2,001	2,140
Refined petroleum products
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	16,157	18,793
Crude oil resales
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	2,877	3,038
Natural gas liquids (NGL)
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	979	1,304
Services and other
Disaggregation of Revenue [Line Items]
Sales and other operating revenues	$ 865	$ (32)