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Regulatory Matters (Narrative) (Detail) ft³ in Millions, customer in Millions, $ in Millions |  | 1 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
May 03, 2019 USD ($) | Nov. 01, 2019 USD ($) | Apr. 30, 2019 ft³ | Mar. 31, 2019 USD ($) | Feb. 28, 2019 USD ($) | Jan. 31, 2019 USD ($) | Oct. 31, 2018 USD ($) | Jul. 31, 2018 USD ($) | Nov. 30, 2013 kV mi | Dec. 31, 2011 | Dec. 31, 2007 customer | Dec. 31, 2018 USD ($)
SCE&G [Member] |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Recover of cost and net lost revenue with incentive |  |  |  |  |  | $ 30 |  |  |  |  |  |
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 amount |  |  |  |  |  |  | $ 13 |  |  |  |  |
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 |  |  |  | $ 135 |  |  |  |  |  |  |  |
Return of equity percentage |  |  |  | 10.75% |  |  |  |  |  |  |  |
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 U |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Proposed revenue requirement |  |  |  | $ 52 |  |  |  |  |  |  |  |
Virginia Electric and Power Company | Virginia Regulation | Rider U | Fourth Phase |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Projected capital investment |  |  |  | $ 123 |  |  |  |  |  |  |  |
Virginia Electric and Power Company | Virginia Regulation | Solar Development Project | Rider US-3 | Operating Segments |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Proposed revenue requirement |  |  |  |  |  |  |  | $ 10 |  |  |  |
Virginia Electric and Power Company | North Carolina Regulation |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Return of equity percentage |  |  |  | 10.75% |  |  |  |  |  |  |  |
Percentage of earned return |  |  |  | 7.52% |  |  |  |  |  |  |  |
Authorized return percentage |  |  |  | 9.90% |  |  |  |  |  |  |  |
Virginia Electric and Power Company | North Carolina Regulation | Scenario Forecast | Annual Base Fuel Revenues |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in revenue requirement |  | $ 27 |  |  |  |  |  |  |  |  |  |
East Ohio | Ohio Regulation | Pipeline Infrastructure Replacement Program |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Proposed revenue requirement |  |  |  |  | $ 190 |  |  |  |  |  |  |
Percentage replacement of pipeline system |  |  |  |  | 25.00% |  |  |  |  |  |  |
Total estimated cost |  |  |  |  | $ 1,600 |  |  |  |  |  |  | $ 202
East Ohio | Ohio Regulation | Automated Meter Reading Program |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Proposed revenue requirement |  |  |  | $ 4 |  |  |  |  |  |  |  |
Number of customers with automated meter reading technology | customer |  |  |  |  |  |  |  |  |  |  | 1.2 |
East Ohio | Ohio Regulation | CEP Program |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Percentage to defer expenses on capital investments |  |  |  |  |  |  |  |  |  | 6.50% |  |
East Ohio | Ohio Regulation | CEP Program | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Proposed revenue requirement | $ 83 |  |  |  |  |  |  |  |  |  |  |
Total estimated cost | $ 723 |  |  |  |  |  |  |  |  |  |  |
Questar Gas | Utah And Wyoming Regulation | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
LNG storage facility, liquefaction rate per day | ft³ |  |  | 8.2 |  |  |  |  |  |  |  |  |
Number of days to make prudency determination |  |  | 180 days |  |  |  |  |  |  |  |  |
Cove Point | Federal Energy Regulatory Commission |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Annual transportation cost rate adjustment, approval amount requested to recover amount |  |  |  |  | $ 24 |  |  |  |  |  |  |

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