Significant Accounting Policies (Depreciation Rates and Estimated Useful Life) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 $ / Mcfe	Dec. 31, 2015	Dec. 31, 2014 USD ($)
Merchant generation-nuclear
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Useful Lives	44 years
Cost of Service Gas and Oil Properties
Public Utility, Property, Plant and Equipment [Line Items]
Cost of service gas and oil properties rate (per Mcfe) | $ / Mcfe	2.08
Virginia Electric and Power Company
Public Utility, Property, Plant and Equipment [Line Items]
Increase in depreciation			$ 38
Increase in depreciation, after tax			$ 23
Generation
Public Utility, Property, Plant and Equipment [Line Items]
Average composite depreciation rates on utility property, plant and equipment (percentage)	2.83%	2.78%	2.66%
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)	2.83%	2.78%	2.66%
Transmission
Public Utility, Property, Plant and Equipment [Line Items]
Average composite depreciation rates on utility property, plant and equipment (percentage)	2.47%	2.42%	2.38%
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)	2.36%	2.33%	2.34%
Transmission | Dominion Gas Holdings, LLC
Public Utility, Property, Plant and Equipment [Line Items]
Average composite depreciation rates on utility property, plant and equipment (percentage)	2.43%	2.46%	2.40%
Distribution
Public Utility, Property, Plant and Equipment [Line Items]
Average composite depreciation rates on utility property, plant and equipment (percentage)	3.02%	3.11%	3.12%
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)	3.32%	3.33%	3.34%
Storage
Public Utility, Property, Plant and Equipment [Line Items]
Average composite depreciation rates on utility property, plant and equipment (percentage)	2.29%	2.42%	2.39%
Storage | Dominion Gas Holdings, LLC
Public Utility, Property, Plant and Equipment [Line Items]
Average composite depreciation rates on utility property, plant and equipment (percentage)	2.19%	2.44%	2.40%
Gas gathering and processing
Public Utility, Property, Plant and Equipment [Line Items]
Average composite depreciation rates on utility property, plant and equipment (percentage)	2.66%	3.19%	2.81%
Gas gathering and processing | Dominion Gas Holdings, LLC
Public Utility, Property, Plant and Equipment [Line Items]
Average composite depreciation rates on utility property, plant and equipment (percentage)	2.58%	3.20%	2.82%
Distribution | Dominion Gas Holdings, LLC
Public Utility, Property, Plant and Equipment [Line Items]
Average composite depreciation rates on utility property, plant and equipment (percentage)	2.55%	2.45%	2.47%
General and other
Public Utility, Property, Plant and Equipment [Line Items]
Average composite depreciation rates on utility property, plant and equipment (percentage)	4.12%	3.67%	3.62%
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)	3.49%	3.40%	3.29%
General and other | Dominion Gas Holdings, LLC
Public Utility, Property, Plant and Equipment [Line Items]
Average composite depreciation rates on utility property, plant and equipment (percentage)	4.54%	4.72%	5.77%
Minimum | Merchant generation-other
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Useful Lives	15 years
Minimum | 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
Minimum | Dominion Gas Holdings, LLC | Gas gathering and processing
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Useful Lives	10 years
Maximum | Merchant generation-other
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Useful Lives	36 years
Maximum | Gas gathering and processing
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Useful Lives	50 years
Maximum | General and other
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Useful Lives	59 years
Maximum | Dominion Gas Holdings, LLC | Gas gathering and processing
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Useful Lives	50 years