Operating Segments and Geographic Data - Segment Revenues (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Sales and other operating revenues	$ 36,117	$ 15,926	$ 67,193	$ 45,631
Oil and Gas
Segment Reporting Information [Line Items]
Sales and other operating revenues	36,117	15,926	67,193	45,631
Oil and Gas | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	43,276	19,085	80,317	56,135
Oil and Gas | All Other
Segment Reporting Information [Line Items]
Sales and other operating revenues	210	233	234	445
Oil and Gas | Total All Other
Segment Reporting Information [Line Items]
Sales and other operating revenues	25	33	49	98
Oil and Gas | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	20,155	8,006	36,824	23,868
Oil and Gas | United States | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(185)	(194)	(185)	(339)
Oil and Gas | United States | All Other
Segment Reporting Information [Line Items]
Sales and other operating revenues	210	227	234	437
Oil and Gas | United States | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(3,941)	(1,946)	(7,262)	(6,163)
Oil and Gas | International | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	23,121	11,079	43,493	32,267
Oil and Gas | International | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	0	(6)	0	(8)
Oil and Gas | International | All Other
Segment Reporting Information [Line Items]
Sales and other operating revenues	0	6	0	8
Oil and Gas | International | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(3,218)	(1,213)	(5,862)	(4,341)
Oil and Gas | Upstream
Segment Reporting Information [Line Items]
Sales and other operating revenues	9,533	4,657	18,884	12,783
Oil and Gas | Upstream | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	15,550	7,098	30,131	20,577
Oil and Gas | Upstream | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	6,034	2,544	11,825	7,010
Oil and Gas | Upstream | United States | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(3,256)	(1,420)	(6,111)	(4,232)
Oil and Gas | Upstream | International | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	9,516	4,554	18,306	13,567
Oil and Gas | Upstream | International | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(2,761)	(1,021)	(5,136)	(3,562)
Oil and Gas | Downstream
Segment Reporting Information [Line Items]
Sales and other operating revenues	26,559	11,236	48,260	32,750
Oil and Gas | Downstream | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	27,516	11,754	49,952	35,113
Oil and Gas | Downstream | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	13,911	5,235	24,765	16,421
Oil and Gas | Downstream | United States | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(500)	(332)	(966)	(1,592)
Oil and Gas | Downstream | International | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	13,605	6,519	25,187	18,692
Oil and Gas | Downstream | International | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	$ (457)	$ (186)	$ (726)	$ (771)