Derivative and Hedging Activities - Marketing Revenues (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018		Sep. 30, 2019	Sep. 30, 2018
Derivative [Line Items]
Revenues	$ 1,003	$ 1,331		$ 3,412	$ 3,924
Losses on undesignated marketing natural gas derivatives	167	(132)		141	(500)
Revenues	2,087	2,424	[1]	6,669	7,237	[1]
Marketing, Gathering And Compression | Other contract
Derivative [Line Items]
Losses on undesignated marketing natural gas derivatives	0	0		(4)	0
Marketing | Marketing, Gathering And Compression
Derivative [Line Items]
Revenues	889	1,219		3,042	3,738
Marketing
Derivative [Line Items]
Revenues	805	1,030		2,773	3,182
Losses on undesignated marketing natural gas derivatives	0			(3)
Revenues	$ 889	$ 1,219	[1]	$ 3,038	$ 3,738	[1]

[1] Financial information for 2018 has been recast to reflect the retrospective application of the successful efforts method of accounting. See Note 1.