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Operating Segments - Virginia Power (Narrative) (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Jun. 30, 2023 | Sep. 30, 2023 | Sep. 30, 2022
Segment Reporting Information [Line Items] |  |  |
Gain (loss) on investments |  | $ 228 | $ (658)
Virginia Electric and Power Company |  |  |
Segment Reporting Information [Line Items] |  |  |
Gain (loss) on investments |  | 31 | (89)
Deferred amounts related to certain riders | Virginia Electric and Power Company |  |  |
Segment Reporting Information [Line Items] |  |  |
Charge for the write-off of certain previously deferred amounts | $ 36 |  |
Charge for the write-off of certain previously deferred amounts, after tax | $ 27 |  |
Operating Segments |  |  |
Segment Reporting Information [Line Items] |  |  |
After- tax net benefits (expenses) |  | 245 | (1,900)
Operating Segments | Nuclear Decommissioning Trust Funds |  |  |
Segment Reporting Information [Line Items] |  |  |
Gain (loss) on investments |  | 183 | (691)
Gain (loss) on investments, after tax |  | 142 | (536)
Operating Segments | Corporate and Other |  |  |
Segment Reporting Information [Line Items] |  |  |
After- tax net benefits (expenses) |  | 26 | (1,000)
After- tax net benefits (expenses) for specific items |  | 231 | (1,000)
Operating Segments | Virginia Electric and Power Company |  |  |
Segment Reporting Information [Line Items] |  |  |
After- tax net benefits (expenses) |  | (154) | (635)
Charge associated with storm damage and service restoration |  |  | 94
Charge associated with storm damage and service restoration, after tax |  |  | 70
Charge for amortization of a regulatory asset, 2021 Triennial Review |  | 183 | 183
Charge for amortization of a regulatory asset, 2021 Triennial Review, after tax |  | 136 | 136
Charge in connection with comprehensive settlement agreement for fuel expenses |  |  | 191
Charge in connection with comprehensive settlement agreement for fuel expenses, after-tax |  |  | 142
Charge for RGGI compliance cost |  |  | 213
Charge for RGGI compliance cost, after tax |  |  | 159
Charges for Dismantling cost |  |  | 60
Charges for Dismantling cost, after tax |  |  | 45
Operating Segments | Virginia Electric and Power Company | Nuclear Decommissioning Trust Funds |  |  |
Segment Reporting Information [Line Items] |  |  |
Gain (loss) on investments |  | 24 | (96)
Gain (loss) on investments, after tax |  | 18 | (71)
Operating Segments | Virginia Electric and Power Company | Corporate and Other |  |  |
Segment Reporting Information [Line Items] |  |  |
After- tax net benefits (expenses) |  | (150) | (601)
After- tax net benefits (expenses) for specific items |  | (156) | $ (641)
Operating Segments | Deferred amounts related to certain riders | Virginia Electric and Power Company |  |  |
Segment Reporting Information [Line Items] |  |  |
Charge for the write-off of certain previously deferred amounts |  | 36 |
Charge for the write-off of certain previously deferred amounts, after tax |  | $ 27 |

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