Operating Segments and Geographic Data - Segment Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Sales and other operating revenues	$ 23,997	$ 34,779	$ 69,628	$ 105,291
Oil and Gas
Segment Reporting Information [Line Items]
Sales and other operating revenues	23,997	34,779	69,628	105,291
Oil and Gas | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	28,285	42,938	84,420	130,044
Oil and Gas | All Other
Segment Reporting Information [Line Items]
Sales and other operating revenues	211	275	656	775
Oil and Gas | Total All Other
Segment Reporting Information [Line Items]
Sales and other operating revenues	37	61	135	187
Oil and Gas | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	11,722	20,096	35,590	59,641
Oil and Gas | United States | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(171)	(209)	(510)	(576)
Oil and Gas | United States | All Other
Segment Reporting Information [Line Items]
Sales and other operating revenues	208	270	645	763
Oil and Gas | United States | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(2,394)	(4,912)	(8,557)	(14,652)
Oil and Gas | International | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	16,563	22,842	48,830	70,403
Oil and Gas | International | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(3)	(5)	(11)	(12)
Oil and Gas | International | All Other
Segment Reporting Information [Line Items]
Sales and other operating revenues	3	5	11	12
Oil and Gas | International | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(1,894)	(3,247)	(6,235)	(10,101)
Oil and Gas | Upstream
Segment Reporting Information [Line Items]
Sales and other operating revenues	5,701	7,508	18,484	23,883
Oil and Gas | Upstream | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	9,278	14,209	29,855	44,364
Oil and Gas | Upstream | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	3,367	5,602	10,377	17,411
Oil and Gas | Upstream | United States | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(1,916)	(3,686)	(6,148)	(11,070)
Oil and Gas | Upstream | International | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	5,911	8,607	19,478	26,953
Oil and Gas | Upstream | International | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(1,661)	(3,015)	(5,223)	(9,411)
Oil and Gas | Downstream
Segment Reporting Information [Line Items]
Sales and other operating revenues	18,259	27,210	51,009	81,221
Oil and Gas | Downstream | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	18,796	28,454	53,909	84,905
Oil and Gas | Downstream | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	8,147	14,224	24,568	41,467
Oil and Gas | Downstream | United States | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	(307)	(1,017)	(1,899)	(3,006)
Oil and Gas | Downstream | International | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues	10,649	14,230	29,341	43,438
Oil and Gas | Downstream | International | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues	$ (230)	$ (227)	$ (1,001)	$ (678)