Annual revenue reduction amount.

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Asset impairment after tax charge.

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Estimated annual revenue reduction on one time customer credit refund.

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Estimated Cost Of Project

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Kilo Volt Line

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Phase-in plan, amount of capitalized costs recoverable.

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Public utilities, amount of disallowance of costs of property, plant and equipment recognized in impairment of assets and other charges.

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Public utilities, amount of disallowance of costs of property, plant and equipment recognized in impairment of assets and other charges, net of tax.

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Public utilities annual revenue reduction amount.

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Public utilities authorized rate percentage.

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Public utilities expected cost to acquire productive assets.

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Public utilities interim rate reduction amount.

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Public utilities, length of transmission line.

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Public utilities number of binding precedent agreements for project Facilities.

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Public utilities operating expense estimated fuel expenses recovered balance.

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Public utilities operating expense estimated fuel expenses recovery.

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Public utilities, property, plant and equipment, expected cost of construction.

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Public Utilities, Requested Rate, Amount

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Recovery Of Projected Deferred Program Costs

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Refund of over recovery of accumulated arrearages.

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Regulatory liabilities one time bill credit refund.

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Amount of recoveries of receivables doubtful of collection that were previously charged off.

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Amount of direct write-downs of accounts receivable charged against the allowance.

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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The increase (decrease) during the period in the costs deferred for rate-making purposes.

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Amount of public utility's approved rate increase (decrease) by regulatory agency.

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Percentage of public utility's approved rate increase (decrease) by regulatory agency.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of public utility's requested rate increase (decrease) with regulatory agency.

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Percentage of public utility's requested return on equity.

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Regulatory Matters (Narrative) (Detail) $ in Millions				1 Months Ended											3 Months Ended		6 Months Ended		12 Months Ended
Regulatory Matters (Narrative) (Detail) $ in Millions	Nov. 01, 2019 USD ($)	Sep. 01, 2019 USD ($)	Jun. 01, 2019 USD ($)	Mar. 31, 2020 USD ($)	Jul. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	May 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jan. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Oct. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Jun. 30, 2015 USD ($) Building	Nov. 30, 2013 kV mi	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Public Utilities General Disclosures [Line Items]
Asset impairment pre tax charge															$ 312	$ 134	$ 1,147	$ 135
Utah Commission \| Scenario Forecast \| Annual Base Fuel Revenues
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement				$ 19
Utah Commission \| Subsequent Event
Public Utilities General Disclosures [Line Items]
Percentage of earned return					9.05%
Authorized return percentage					9.85%
Return of equity percentage					10.50%
DETI
Public Utilities General Disclosures [Line Items]
Disallowance of costs of property, plant and equipment																129
Disallowance of costs of property, plant and equipment, net of tax																$ 94
DETI \| Federal Energy Regulatory Commission \| Supply Header Project
Public Utilities General Disclosures [Line Items]
Asset impairment pre tax charge															13
Asset impairment after tax charge						$ 10									10		10
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Submitted and approved decrease in base rate revenue											$ 14
Regulatory liabilities one time bill credit reduction amount															13
Asset impairment pre tax charge															197		$ 743
Virginia Electric and Power Company \| Virginia Regulation
Public Utilities General Disclosures [Line Items]
Proposed annual revenue reduction amount									$ 171
Interim rate reduction amount												$ 125
Annual revenue reduction amount								$ 183
Estimated annual revenue reduction on one-time customer credit															$ 132
Proposed revenue requirement							$ 1,500
Proposed revenue requirement recovered balance			$ 107				124
Increase (decrease) in revenue requirement			$ (254)				(192)
Virginia Electric and Power Company \| Virginia Regulation \| Surry Switching Station Transmission Line
Public Utilities General Disclosures [Line Items]
Length of transmission line (miles) \| mi														7
Capacity of transmission line (kV) \| kV														500
Virginia Electric and Power Company \| Virginia Regulation \| Transmission Line from Skiffes Creek Switching Station to Wheaton Substation
Public Utilities General Disclosures [Line Items]
Length of transmission line (miles) \| mi														20
Capacity of transmission line (kV) \| kV														230
Virginia Electric and Power Company \| Virginia Regulation \| Rider T1
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement							271
Proposed revenue requirement							920
Virginia Electric and Power Company \| Virginia Regulation \| Rider T1 \| Scenario Forecast
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement		$ 446
Virginia Electric and Power Company \| Virginia Regulation \| Rider T1 \| Transmission Component Of Base Rates
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement							474
Virginia Electric and Power Company \| Virginia Regulation \| Solar Development Project \| Subsequent Event
Public Utilities General Disclosures [Line Items]
Total estimated capital investment					$ 146
Virginia Electric and Power Company \| Virginia Regulation \| Solar Development Project \| Rider US-4 \| Operating Segments \| Subsequent Event
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement					$ 9
DESC \| South Carolina Regulation
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement						7
Proposed revenue requirement						$ 437
East Ohio \| Ohio Regulation \| Percentage Of Income Payment Plan Rider
Public Utilities General Disclosures [Line Items]
Refund of over-recovery of accumulated arrearages							12
Recovery of projected deferred program costs							$ 8
East Ohio \| Ohio Regulation \| UEX Rider
Public Utilities General Disclosures [Line Items]
Elimination of over-recovered balance of accumulated bad debt expense								$ 3
East Ohio \| Ohio Regulation \| Scenario Forecast \| UEX Rider
Public Utilities General Disclosures [Line Items]
Recovery of prospective net bad debt expense																				$ 15
Hope Gas, Inc. \| West Virginia Regulation \| Scenario Forecast \| PREP
Public Utilities General Disclosures [Line Items]
Projected capital investment																			$ 39		$ 29
Amount of cost recovery	$ 10
Cove Point \| West Virginia Regulation \| PREP
Public Utilities General Disclosures [Line Items]
Amount of cost recovery																						$ 30
Cove Point \| Federal Energy Regulatory Commission
Public Utilities General Disclosures [Line Items]
Public utilities expected cost to acquire productive assets													$ 150
Public utilities number of binding precedent agreements for project facilities \| Building													2
Estimated Cost of project										$ 45
Asset impairment pre tax charge										37
Asset impairment after tax charge										$ 28												$ 28