Sales and Other Operating Revenues - Disaggregated (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from External Customer [Line Items]
Sales and Other Operating Revenues	$ 16,409	$ 15,929	$ 10,913	$ 20,878	$ 29,125	$ 27,218	$ 27,847	$ 23,103	$ 64,129	$ 107,293	$ 111,461
United States
Revenue from External Customer [Line Items]
Sales and Other Operating Revenues									48,711	83,512	86,401
United Kingdom
Revenue from External Customer [Line Items]
Sales and Other Operating Revenues									7,031	9,863	11,054
Germany
Revenue from External Customer [Line Items]
Sales and Other Operating Revenues									3,034	4,053	4,352
Other foreign countries
Revenue from External Customer [Line Items]
Sales and Other Operating Revenues									5,353	9,865	9,654
Refined petroleum products
Revenue from External Customer [Line Items]
Sales and Other Operating Revenues									49,768	87,902	87,967
Crude oil resales
Revenue from External Customer [Line Items]
Sales and Other Operating Revenues									9,114	14,125	16,419
NGL
Revenue from External Customer [Line Items]
Sales and Other Operating Revenues									4,084	4,814	6,161
Services and other
Revenue from External Customer [Line Items]
Sales and Other Operating Revenues									$ 1,163	$ 452	$ 914