Short-Term Debt and Credit Facilities - EEGH - Credit Facility (Details) - USD ($)		Dec. 31, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Line of credit maximum borrowing capacity	[1]	$ 11,030,000,000	$ 9,412,000,000
Short-term debt	[1]	2,286,000,000	3,214,000,000
Eastern Energy Gas Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Short-term debt		$ 0	$ 62,000,000
Eastern Energy Gas Holdings, LLC [Member] | Commercial Paper [Member]
Line of Credit Facility [Line Items]
Weighted average interest rate			1.98%
Short-term debt			$ 62,000,000
Eastern Energy Gas Holdings, LLC [Member] | Joint Revolving Credit Facility With Dominion Energy [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit maximum borrowing capacity			1,500,000,000
Line of credit sub-limit			$ 750,000,000

[1] The table does not include unused credit facilities and letters of credit for investments that are accounted for under the equity method.