Sales and Other Operating Revenue - Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue from contracts with customers	$ 9,556	$ 2,749	$ 19,382	$ 8,907
Customers within the scope of ASC Topic 606 [Member]
Revenue from contracts with customers	7,753	1,919	14,914	6,830
Physical gas contracts [Member]
Revenue from contracts with customers	1,754	856	4,728	2,152
Crude oil product line [Member]
Revenue from contracts with customers	178	26	302	118
Natural Gas Product Line [Member]
Revenue from contracts with customers	1,504	763	4,231	1,853
Other Products [Member]
Revenue from contracts with customers	72	67	195	181
Financial Derivative Contracts [Member]
Revenue from contracts with customers	49	(26)	(260)	(75)
Lower 48 Segment \| Physical gas contracts [Member]
Revenue from contracts with customers	1,345	698	3,811	1,674
Canada Segment [Member] \| Physical gas contracts [Member]
Revenue from contracts with customers	207	121	510	300
Europe, Middle East and North Africa [Member] \| Physical gas contracts [Member]
Revenue from contracts with customers	$ 202	$ 37	$ 407	$ 178