Property, Plant and Equipment (Table of Property and Equipment, net) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Property and equipment:
Proved		$ 27,589	$ 27,668
Unproved and properties under development		392	583
Total oil and gas		27,981	28,251
Less accumulated DD&A		(23,545)	(20,693)
Oil and gas property and equipment, net		4,436	7,558
Other property and equipment		1,737	1,725
Less accumulated DD&A		(780)	(690)
Other property and equipment, net	[1]	957	1,035
Total property and equipment, net		$ 5,393	$ 8,593

[1] $102 million and $80 million related to CDM in 2020 and 2019, respectively