Regulatory Matters (Narrative) (Details) customer in Millions	1 Months Ended																					3 Months Ended	12 Months Ended						108 Months Ended
	Feb. 28, 2017 USD ($)	Dec. 31, 2016 USD ($) Rate MW	Nov. 30, 2016 USD ($)	Oct. 31, 2016 USD ($) program	Sep. 30, 2016 USD ($)	Aug. 31, 2016 USD ($) kV mi	Jul. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	May 31, 2016 USD ($)	Apr. 30, 2016 USD ($) program	Mar. 31, 2016 USD ($) kV mi	Feb. 29, 2016 USD ($) kV	Nov. 30, 2015 USD ($) kV mi	Apr. 30, 2015 kV	Mar. 31, 2015 USD ($)	Feb. 28, 2015 test_period	Nov. 30, 2013 kV mi	May 31, 2012 USD ($)	Mar. 31, 2010 USD ($)	Aug. 31, 2009 kV	Apr. 30, 2007 kV	Dec. 31, 2017 USD ($) MW	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) power_station	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2008	Dec. 31, 2007 customer	Dec. 31, 2016 USD ($)	Jan. 31, 2017 USD ($)
Public Utilities, General Disclosures [Line Items]
Regulatory asset		$ 2,717,000,000																						$ 2,717,000,000	$ 2,216,000,000				$ 2,717,000,000
Charge recognized																								0	0	$ 374,000,000
Total amount of credit to customers		2,785,000,000																						2,785,000,000	2,385,000,000				$ 2,785,000,000
Project Cost																								40,000,000	418,000,000	206,000,000
Virginia Electric and Power Company
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage																													11.40%
Costs claimed to be unjust and excluded from transmission formula rate																			$ 223,000,000
Potential settlement required annual payment for 10 years																		$ 250,000
Settlement payment duration																		10 years
Regulatory asset		949,000,000																						949,000,000	993,000,000				$ 949,000,000
Charge recognized																								0	0	374,000,000
Total amount of credit to customers		$ 2,077,000,000																						2,077,000,000	1,964,000,000				2,077,000,000
Project Cost																								7,000,000	43,000,000	$ 0
Virginia Electric and Power Company | Minimum
Public Utilities, General Disclosures [Line Items]
Facility operating capacity (kV) | kV																				500	500
Virginia Electric and Power Company | Virginia Regulation | Solar Development Project | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Total estimate cost	$ 47,000,000
Virginia Electric and Power Company | Virginia Regulation | North Anna | Intent to Sue Notification Received from Sierra Club Alleging Endangered Species Act Violations
Public Utilities, General Disclosures [Line Items]
Period of notice of intent to sue						60 days
Virginia Electric and Power Company | Virginia Regulation | Phase One of Cost Recovery to Move Electric Distribution Facilities Underground
Public Utilities, General Disclosures [Line Items]
Estimated cost of project						$ 140,000,000
Virginia Electric and Power Company | Virginia Regulation | Surry Switching Station Transmission Line
Public Utilities, General Disclosures [Line Items]
Length of transmission line (in miles) | mi																	7
KV Line (in 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 (in miles) | mi																	20
KV Line (in kv) | kV																	230
Virginia Electric and Power Company | Virginia Regulation | Surry to Skiffes Creek Transmission Line
Public Utilities, General Disclosures [Line Items]
KV Line (in kv) | kV														500
Virginia Electric and Power Company | Virginia Regulation | Poland Road Substation
Public Utilities, General Disclosures [Line Items]
KV Line (in kv) | kV						230
Virginia Electric and Power Company | Virginia Regulation | Double Circuit Transmission Line between Loudoun-Brambleton Line and Poland Road Substation
Public Utilities, General Disclosures [Line Items]
Length of transmission line (in miles) | mi						4
KV Line (in kv) | kV						230
Virginia Electric and Power Company | Virginia Regulation | Loudoun- Brambleton Line to Poland Road Substation
Public Utilities, General Disclosures [Line Items]
Total estimate cost						$ 55,000,000
Virginia Electric and Power Company | Virginia Regulation | Loudoun- Brambleton Line
Public Utilities, General Disclosures [Line Items]
KV Line (in kv) | kV						230
Virginia Electric and Power Company | Virginia Regulation | Transmission Line Near Gainesville Substation and Haymarket Substation
Public Utilities, General Disclosures [Line Items]
Total estimate cost													$ 55,000,000
Length of transmission line (in miles) | mi													5
KV Line (in kv) | kV													230
Virginia Electric and Power Company | Virginia Regulation | Transmission Line between Remington and Gordonsville Substations
Public Utilities, General Disclosures [Line Items]
Total estimate cost													$ 105,000,000
Length of transmission line (in miles) | mi													38
KV Line (in kv) | kV													230
Virginia Electric and Power Company | Virginia Regulation | Remington CT-Warrenton, Vint Hill-Wheeler, and Wheeler Gainesville Transmission Lines, and Vint Hill and Wheeler Switching Stations
Public Utilities, General Disclosures [Line Items]
Total estimate cost												$ 110,000,000
Virginia Electric and Power Company | Virginia Regulation | Remington CT Warrenton Double Circuit Transmission Line
Public Utilities, General Disclosures [Line Items]
KV Line (in kv) | kV												230
Virginia Electric and Power Company | Virginia Regulation | Vint Hill-Wheeler and Wheeler Gainesville Lines
Public Utilities, General Disclosures [Line Items]
KV Line (in kv) | kV												230
Virginia Electric and Power Company | Virginia Regulation | Vint Hill and Wheeler Switching Stations
Public Utilities, General Disclosures [Line Items]
KV Line (in kv) | kV												230
Virginia Electric and Power Company | Virginia Regulation | Transmission Line between Cunningham switching station and Dooms substation
Public Utilities, General Disclosures [Line Items]
Total estimate cost											$ 60,000,000
Length of transmission line (in miles) | mi											33
KV Line (in kv) | kV											500
Virginia Electric and Power Company | Virginia Regulation | Transmission Line between Carson switching station a terminus near Rogers Road Switching Station
Public Utilities, General Disclosures [Line Items]
Total estimate cost						$ 55,000,000
Length of transmission line (in miles) | mi						28
KV Line (in kv) | kV						500
Virginia Electric and Power Company | Virginia Regulation | Idylwood substation | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Total estimate cost																														$ 110,000,000
Virginia Electric and Power Company | Virginia Regulation | February 2015 Regulation Act Legislation
Public Utilities, General Disclosures [Line Items]
Number of test periods | test_period																5
Virginia Electric and Power Company | Virginia Regulation | February 2015 Regulation Act Legislation | Minimum
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage												9.60%
Virginia Electric and Power Company | Virginia Regulation | Rider GV
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage											9.60%
Proposed revenue requirement								$ 89,000,000
Increase (decrease) in revenue requirement								$ 49,000,000
Approved revenue requirement											$ 40,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider GV | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage	9.40%
Virginia Electric and Power Company | Virginia Regulation | Rider GV | Minimum
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage											9.60%
Virginia Electric and Power Company | Virginia Regulation | Rider GV | Minimum | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage	9.40%
Virginia Electric and Power Company | Virginia Regulation | Riders C1A and C2A
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage										9.60%
Proposed revenue requirement				$ 45,000,000
Approved revenue requirement										$ 46,000,000
Number of new energy efficiency programs | program										1
Virginia Electric and Power Company | Virginia Regulation | Riders C1A and C2A | Minimum
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage										9.60%
Virginia Electric and Power Company | Virginia Regulation | Riders C1A and C2A | Energy Efficiency Program
Public Utilities, General Disclosures [Line Items]
Number of new energy efficiency programs | program				2
Period for cost cap				5 years
Extension period for cost cap				2 years
Virginia Electric and Power Company | Virginia Regulation | Riders C1A and C2A | Energy Efficiency Program | Maximum
Public Utilities, General Disclosures [Line Items]
Deferred fuel balance				$ 178,000,000
Virginia Electric and Power Company | Virginia Regulation | Riders C1A and C2A | Peak Shaving Program
Public Utilities, General Disclosures [Line Items]
Extension period for cost cap				5 years
Virginia Electric and Power Company | Virginia Regulation | Riders C1A and C2A | Peak Shaving Program | Maximum
Public Utilities, General Disclosures [Line Items]
Deferred fuel balance				$ 5,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider BW
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage								10.60%
Proposed revenue requirement				134,000,000
Increase (decrease) in revenue requirement				15,000,000
Approved revenue requirement								$ 119,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider BW | Minimum
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage								9.60%
Virginia Electric and Power Company | Virginia Regulation | Rider US-2
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage								9.60%
Proposed revenue requirement				10,000,000
Increase (decrease) in revenue requirement				$ 6,000,000
Approved revenue requirement								$ 4,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider US-2 | Minimum
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage								9.60%
Virginia Electric and Power Company | Virginia Regulation | Rider US-2 | Solar Development Project
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage								9.60%
Capacity of solar facility (in MW) | MW		56
Approved revenue requirement								$ 4,000,000
Project Cost		$ 130,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider U
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage						9.60%
Proposed revenue requirement		31,000,000
Approved revenue requirement						$ 20,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider U | Minimum
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage						9.60%
Virginia Electric and Power Company | Virginia Regulation | Rider U | Phase One of Cost Recovery to Move Electric Distribution Facilities Underground
Public Utilities, General Disclosures [Line Items]
Deferred fuel balance						$ 123,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider U | Rider U- Phase Two Project
Public Utilities, General Disclosures [Line Items]
Estimated cost of project		110,000,000																						$ 110,000,000					110,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider U, 2017-2018 Rate Year
Public Utilities, General Disclosures [Line Items]
Projected capital investment						2,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider U, 2018-2019 Rate Year
Public Utilities, General Disclosures [Line Items]
Projected capital investment						2,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider B
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage												11.60%
Proposed revenue requirement								28,000,000
Increase (decrease) in revenue requirement								(2,000,000)
Approved revenue requirement												$ 30,000,000
Number of power stations converted to biomass | power_station																								3
Virginia Electric and Power Company | Virginia Regulation | Rider B | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage	11.40%
Virginia Electric and Power Company | Virginia Regulation | Rider B | Minimum | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage	9.40%
Virginia Electric and Power Company | Virginia Regulation | Rider R
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage												10.60%
Proposed revenue requirement								75,000,000
Increase (decrease) in revenue requirement								1,000,000
Approved revenue requirement												$ 74,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider R | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage	10.40%
Virginia Electric and Power Company | Virginia Regulation | Rider R | Minimum | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage	9.40%
Virginia Electric and Power Company | Virginia Regulation | Rider S
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage												10.60%
Proposed revenue requirement								254,000,000
Increase (decrease) in revenue requirement								3,000,000
Approved revenue requirement												$ 251,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider S | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage	10.40%
Virginia Electric and Power Company | Virginia Regulation | Rider S | Minimum | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage	9.40%
Virginia Electric and Power Company | Virginia Regulation | Rider W
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage												10.60%
Proposed revenue requirement								126,000,000
Increase (decrease) in revenue requirement								8,000,000
Approved revenue requirement												$ 118,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider W | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage	10.40%
Virginia Electric and Power Company | Virginia Regulation | Rider W | Minimum | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage	9.40%
Virginia Electric and Power Company | Virginia Regulation | Virginia Commission 2015 Biennial Review
Public Utilities, General Disclosures [Line Items]
Approved ROE percentage													10.00%
Earned ROE percentage													10.89%
ROE above authorized ROE (basis points)													0.70%
Duration excess earnings will be credited to customers													6 months
Period after Biennial Review Order													60 days
Virginia Electric and Power Company | Virginia Regulation | Virginia Commission 2015 Biennial Review | Revenue Subject to Refund
Public Utilities, General Disclosures [Line Items]
Total amount of credit to customers													$ 20,000,000
Virginia Electric and Power Company | Virginia Regulation | Annual Fuel Factor Submitted to the Virginia Commission
Public Utilities, General Disclosures [Line Items]
Proposed revenue requirement									$ 1,400,000,000
Increase (decrease) in revenue requirement									(286,000,000)
Virginia Electric and Power Company | Virginia Regulation | Application filed with Virginia Commission to Construct and Operate the Oceana Solar Facility | Solar Development Project | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Capacity of solar facility (in MW) | MW																						18
Project Cost																						$ 40,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider T1
Public Utilities, General Disclosures [Line Items]
Proposed revenue requirement									639,000,000
Increase (decrease) in revenue requirement									1,000,000
Virginia Electric and Power Company | North Carolina Regulation | Annual Non- Fuel Base Revenues
Public Utilities, General Disclosures [Line Items]
Increase (decrease) in revenue requirement											$ 51,000,000
Proposed ROE percentage				9.90%							10.50%
Amount of base rate increase				$ 35,000,000
Virginia Electric and Power Company | North Carolina Regulation | Annual Base Fuel Revenues
Public Utilities, General Disclosures [Line Items]
Increase (decrease) in revenue requirement						(36,000,000)
Additional reduction approved in annual filing		1,000,000
Virginia Electric and Power Company | FERC | Settled Litigation | Order Regarding Transmission Rate Design for Allocation of Costs among PJM Interconnect LLC Transmission Customers | Legislation enacted
Public Utilities, General Disclosures [Line Items]
Settlement amount								$ 200,000,000
Settlement payment period								10 years
Virginia Electric and Power Company | FERC | Settled Litigation | Order Regarding Transmission Rate Design for Allocation of Costs among PJM Interconnect LLC Transmission Customers | Legislation enacted | Regulatory Asset for contingent liability
Public Utilities, General Disclosures [Line Items]
Regulatory asset		192,000,000																						$ 192,000,000					192,000,000
Virginia Electric and Power Company | FERC | Settled Litigation | Order Regarding Transmission Rate Design for Allocation of Costs among PJM Interconnect LLC Transmission Customers | Legislation enacted | Other operations and maintenance expense
Public Utilities, General Disclosures [Line Items]
Charge recognized																								8,000,000
Virginia Electric and Power Company | FERC | Settled Litigation | Order Regarding Transmission Rate Design for Allocation of Costs among PJM Interconnect LLC Transmission Customers | Legislation enacted | Other Deferred Credits and Other Liabilities
Public Utilities, General Disclosures [Line Items]
Amount of accrued liability		$ 200,000,000																						200,000,000					$ 200,000,000
East Ohio | Ohio Regulation | PIR Program
Public Utilities, General Disclosures [Line Items]
Proposed revenue requirement												131,000,000
Estimated cost of project															$ 200,000,000
Percentage replacement of pipeline system																											25.00%
Period for capital investment															5 years
Total estimated cost												1,000,000,000													$ 171,000,000
Annual percentage increase in capital investment															3.00%
East Ohio | Ohio Regulation | AMR Program
Public Utilities, General Disclosures [Line Items]
Proposed revenue requirement												$ 7,000,000
Number of customers with automated meter reading technology | customer																												1.2
East Ohio | Ohio Regulation | PIPP Plus Program
Public Utilities, General Disclosures [Line Items]
Refund of overrecovery of accumulated arrearages							$ 32,000,000
Recovery of projected deferred program costs							$ 28,000,000
East Ohio | Ohio Regulation | UEX Rider
Public Utilities, General Disclosures [Line Items]
Elimination of over-recovered balance of accumulated bad debt expense						8,000,000
Prospective bad debt expense recovered						$ 19,000,000
East Ohio | Ohio Regulation | PSMP
Public Utilities, General Disclosures [Line Items]
Estimated cost of project			$ 15,000,000
Hope Gas Inc | West Virginia Regulation | PREP
Public Utilities, General Disclosures [Line Items]
Projected capital investment																								$ 20,000,000
Estimated cost of project									$ 152,000,000
Deferred fuel balance					$ 2,000,000
Period for capital investment									5 years
Hope Gas Inc | West Virginia Regulation | PREP | Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Projected capital investment																							$ 27,000,000
Cove Point | FERC
Public Utilities, General Disclosures [Line Items]
Proposed revenue requirement			$ 140,000,000
Number of proposed rates that were suspended | Rate		5