Regulatory Matters (Other Regulatory Matters Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Public Utilities, General Disclosures [Line Items]
Equity in losses of unconsolidated affiliates	$ 2,005	$ (162)	$ (83)
Income tax expense (benefit) from continuing operations	(236)	519	$ 448
Other	2,936	2,367
Asset retirement obligations	$ 718	$ 881
Atlantic Coast Pipeline (ACP)
Public Utilities, General Disclosures [Line Items]
Joint owner ownership percentage	47.00%
Atlantic Coast Pipeline (ACP) | Atlantic Coast Pipeline (ACP)
Public Utilities, General Disclosures [Line Items]
Equity in losses of unconsolidated affiliates	$ 2,100
Income tax expense (benefit) from continuing operations	393
Restructuring and related cost, expected cost	20
Other	928
Other liabilities, noncurrent	8
Atlantic Coast Pipeline (ACP) | Atlantic Coast Pipeline (ACP) | Current Liabilities
Public Utilities, General Disclosures [Line Items]
Face value of guarantees	860
Asset retirement obligations	$ 76