Property, Plant and Equipment (Summary of Property and Equipment, net) (Details) - USD ($) $ in Millions		Mar. 31, 2021	Dec. 31, 2020
Property and equipment:
Proved		$ 35,119	$ 27,589
Unproved and properties under development		2,692	392
Total oil and gas		37,811	27,981
Less accumulated DD&A		(23,985)	(23,545)
Oil and gas property and equipment, net		13,826	4,436
Other property and equipment		2,060	1,737
Less accumulated DD&A		(612)	(780)
Other property and equipment, net	[1]	1,448	957
Total property and equipment, net		$ 15,274	$ 5,393

[1] $106 million and $102 million related to CDM in 2021 and 2020, respectively.