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Significant Accounting Policies (Depreciation Rates and Estimated Useful Life) (Detail) | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Merchant Generation Nuclear |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives | 44 years |  |
LNG Facility [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives | 40 years |  |
Minimum | Merchant Generation-Other |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives | 15 years |  |
Minimum | Nonutility Gas Gathering and Processing |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives | 3 years |  |
Minimum | General and Other |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives | 5 years |  |
Maximum | Merchant Generation-Other |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives | 30 years |  |
Maximum | Nonutility Gas Gathering and Processing |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives | 50 years |  |
Maximum | Nonutility Gas Gathering and Processing | Dominion Energy Gas Holdings, LLC |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives | 40 years |  |
Maximum | General and Other |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated useful lives | 59 years |  |
Generation |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average composite depreciation rates on utility property, plant and equipment (percentage) | 2.84% | 2.71% | 2.94%
Generation | Virginia Electric and Power Company |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average composite depreciation rates on utility property, plant and equipment (percentage) | 2.94% | 2.71% | 2.94%
Transmission |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average composite depreciation rates on utility property, plant and equipment (percentage) | 2.47% | 2.54% | 2.55%
Transmission | Virginia Electric and Power Company |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average composite depreciation rates on utility property, plant and equipment (percentage) | 2.54% | 2.52% | 2.54%
Transmission | Dominion Energy Gas Holdings, LLC |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average composite depreciation rates on utility property, plant and equipment (percentage) | 2.43% | 2.66% | 2.67%
Distribution |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average composite depreciation rates on utility property, plant and equipment (percentage) | 2.80% | 2.97% | 3.00%
Distribution | Virginia Electric and Power Company |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average composite depreciation rates on utility property, plant and equipment (percentage) | 3.14% | 3.31% | 3.32%
Storage |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average composite depreciation rates on utility property, plant and equipment (percentage) | 2.40% | 2.40% | 2.48%
Storage | Dominion Energy Gas Holdings, LLC |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average composite depreciation rates on utility property, plant and equipment (percentage) | 2.53% | 2.42% | 2.51%
General and Other |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average composite depreciation rates on utility property, plant and equipment (percentage) | 4.04% | 4.20% | 4.38%
General and Other | Virginia Electric and Power Company |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average composite depreciation rates on utility property, plant and equipment (percentage) | 4.40% | 4.52% | 4.68%
General and Other | Dominion Energy Gas Holdings, LLC |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Average composite depreciation rates on utility property, plant and equipment (percentage) | 4.59% | 4.18% | 5.08%

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