Regulatory Matters - EEGH - Other Regulatory Matters (Details) dekathermPerDay in Thousands, $ in Millions		1 Months Ended					3 Months Ended
	Aug. 01, 2020 USD ($)	Jan. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) dekathermPerDay	Dec. 31, 2018 USD ($)	Jun. 30, 2015 USD ($) dekathermPerDay agreement	Dec. 31, 2014 dekathermPerDay	Oct. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2020 USD ($)
Regulatory Liabilities [Line Items]
Regulatory Liabilities			$ 7,311								$ 7,475
Asset Retirement Obligation Costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities			$ 241								305
Cove Point LNG, LP [Member] | Federal Energy Regulatory Commission [Member]
Regulatory Liabilities [Line Items]
Number of binding precedent agreements | agreement					2
Cost to acquire project				$ 45	$ 150
Impairment of assets				37
Impairment of assets, after-tax				$ 28
Firm transportation service (Dth per day) | dekathermPerDay					150
Cove Point LNG, LP [Member] | Federal Energy Regulatory Commission [Member] | General Rate Case [Member]
Regulatory Liabilities [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 182
Cove Point LNG, LP [Member] | Federal Energy Regulatory Commission [Member] | General Rate Case, Increase In Revenue [Member]
Regulatory Liabilities [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 4
Cove Point LNG, LP [Member] | Federal Energy Regulatory Commission [Member] | General Rate Case, Decrease In Depreciation Expense [Member]
Regulatory Liabilities [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ (1)
Cove Point LNG, LP [Member] | Federal Energy Regulatory Commission [Member] | General Rate Case, Provision [Member]
Regulatory Liabilities [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount							$ 7
Eastern Gas Transmission and Storage, Inc. [Member] | Cancellation Of Atlantic Coast Pipeline Project [Member]
Regulatory Liabilities [Line Items]
Impairment of assets									$ 482
Impairment of assets, after-tax									359
Eastern Gas Transmission and Storage, Inc. [Member] | Atlantic Coast Pipeline Project, Available For Potential Modified Project [Member]
Regulatory Liabilities [Line Items]
Impairment of assets								$ 10
Impairment of assets, after-tax								7
Benefit from ARO revision								29
Benefit from ARO revision, after-tax								$ 20
Property, plant and equipment, net											40
Eastern Gas Transmission and Storage, Inc. [Member] | Cancellation Of Sweden Valley Project [Member]
Regulatory Liabilities [Line Items]
Impairment of assets										$ 13
Impairment of assets, after-tax										10
Eastern Gas Transmission and Storage, Inc. [Member] | Federal Energy Regulatory Commission [Member]
Regulatory Liabilities [Line Items]
Firm transportation service (Dth per day) | dekathermPerDay						1,500
Eastern Gas Transmission and Storage, Inc. [Member] | Federal Energy Regulatory Commission [Member] | Transportation Service To Tennessee Gas Pipeline Company [Member]
Regulatory Liabilities [Line Items]
Firm transportation service (Dth per day) | dekathermPerDay			120
Eastern Gas Transmission and Storage, Inc. [Member] | Federal Energy Regulatory Commission [Member] | Cost Of Project For Transportation Service To Tennessee Gas Pipeline Company [Member]
Regulatory Liabilities [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount										$ 17
Eastern Gas Transmission and Storage, Inc. [Member] | Asset Retirement Obligation Costs | Atlantic Coast Pipeline Project, Available For Potential Modified Project [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities									$ 75
Eastern Energy Gas Holdings, LLC [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			$ 841								709
Property, plant and equipment, net			$ 11,727								$ 10,144