Fair Value Measurements (Fair Value, Option, Quantitative Disclosures) (Details) $ in Millions		9 Months Ended
		Sep. 30, 2016 USD ($) $ / MWh $ / MMBTU	Dec. 31, 2015 USD ($)
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		$ 295	$ 388
Fair Value of Derivative Liabilities		422	343
Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		118	127
Fair Value of Derivative Liabilities		291	86
Dominion Gas Holdings, LLC
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		14	11
Fair Value of Derivative Liabilities		6	14
Level 3 | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		90
Fair Value, Measurements, Recurring | Physical and financial forwards and futures:
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		268	364
Fair Value of Derivative Liabilities		111	160
Fair Value, Measurements, Recurring | Virginia Electric and Power Company | Physical and financial forwards and futures:
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		116	114
Fair Value of Derivative Liabilities		24	27
Fair Value, Measurements, Recurring | Dominion Gas Holdings, LLC | Physical and financial forwards and futures:
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		6	11
Fair Value of Derivative Liabilities		2
Fair Value, Measurements, Recurring | Level 3
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		96
Fair Value of Derivative Liabilities		7
Fair Value, Measurements, Recurring | Level 3 | Physical and financial forwards and futures:
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		96	114
Fair Value of Derivative Liabilities		7	19
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Natural Gas | Physical and financial forwards and futures:
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets	[1]	85
Fair Value of Derivative Liabilities	[1]	$ 4
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Natural Gas | Liabilities | Physical and financial forwards and futures: | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[2]	(2)
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Natural Gas | Liabilities | Physical and financial forwards and futures: | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[2]	4
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Natural Gas | Liabilities | Physical and financial forwards and futures: | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[2],[3]	1
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Natural Gas | Assets | Physical and financial forwards and futures: | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[2]	(2)
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Natural Gas | Assets | Physical and financial forwards and futures: | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[2]	7
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Natural Gas | Assets | Physical and financial forwards and futures: | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU		0
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | FTRs | Physical and financial forwards and futures:
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		$ 7
Fair Value of Derivative Liabilities		$ 2
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | FTRs | Liabilities | Physical and financial forwards and futures: | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MWh	[2]	(11)
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | FTRs | Liabilities | Physical and financial forwards and futures: | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MWh	[2]	6
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | FTRs | Liabilities | Physical and financial forwards and futures: | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MWh	[2],[3]	1
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | FTRs | Assets | Physical and financial forwards and futures: | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MWh	[2]	(6)
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | FTRs | Assets | Physical and financial forwards and futures: | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MWh	[2]	6
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | FTRs | Assets | Physical and financial forwards and futures: | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MWh	[2],[3]	1
Fair Value, Measurements, Recurring | Level 3 | Option model | Natural Gas | Physical and financial options:
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		$ 4
Fair Value of Derivative Liabilities		$ 1
Fair Value, Measurements, Recurring | Level 3 | Option model | Natural Gas | Liabilities | Physical and financial options: | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[2]	2
Price volatility percentage	[4]	30.00%
Fair Value, Measurements, Recurring | Level 3 | Option model | Natural Gas | Liabilities | Physical and financial options: | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[2]	4
Price volatility percentage	[4]	46.00%
Fair Value, Measurements, Recurring | Level 3 | Option model | Natural Gas | Liabilities | Physical and financial options: | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[2],[3]	3
Price volatility percentage	[3],[4]	38.00%
Fair Value, Measurements, Recurring | Level 3 | Option model | Natural Gas | Assets | Physical and financial options: | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[2]	2
Price volatility percentage	[4]	19.00%
Fair Value, Measurements, Recurring | Level 3 | Option model | Natural Gas | Assets | Physical and financial options: | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[2]	7
Price volatility percentage	[4]	46.00%
Fair Value, Measurements, Recurring | Level 3 | Option model | Natural Gas | Assets | Physical and financial options: | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[2],[3]	3
Price volatility percentage	[3],[4]	24.00%
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Liabilities		$ 2
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Physical and financial forwards and futures:
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		90	101
Fair Value of Derivative Liabilities		2	8
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Discounted cash flow | Natural Gas | Physical and financial forwards and futures:
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets	[5]	$ 81
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Discounted cash flow | Natural Gas | Assets | Physical and financial forwards and futures: | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[6]	(2)
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Discounted cash flow | Natural Gas | Assets | Physical and financial forwards and futures: | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[6]	7
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Discounted cash flow | Natural Gas | Assets | Physical and financial forwards and futures: | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[6],[7]	0
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Discounted cash flow | FTRs | Physical and financial forwards and futures:
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		$ 7
Fair Value of Derivative Liabilities		$ 2
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Discounted cash flow | FTRs | Liabilities | Physical and financial forwards and futures: | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MWh	[6]	(11)
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Discounted cash flow | FTRs | Liabilities | Physical and financial forwards and futures: | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MWh	[6]	6
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Discounted cash flow | FTRs | Liabilities | Physical and financial forwards and futures: | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MWh	[6],[7]	1
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Discounted cash flow | FTRs | Assets | Physical and financial forwards and futures: | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MWh	[6]	(6)
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Discounted cash flow | FTRs | Assets | Physical and financial forwards and futures: | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MWh	[6]	6
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Discounted cash flow | FTRs | Assets | Physical and financial forwards and futures: | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MWh	[6],[7]	1
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Option model | Natural Gas | Physical and financial options:
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		$ 2
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Option model | Natural Gas | Assets | Physical and financial options: | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[6]	2
Price volatility percentage	[8]	19.00%
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Option model | Natural Gas | Assets | Physical and financial options: | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[6]	7
Price volatility percentage	[8]	33.00%
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | Option model | Natural Gas | Assets | Physical and financial options: | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Market price (per Dth, per MWh) | $ / MMBTU	[6],[7]	3
Price volatility percentage	[7],[8]	24.00%
Fair Value, Measurements, Recurring | Level 3 | Dominion Gas Holdings, LLC | Physical and financial forwards and futures:
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		$ 0	$ 6
Fair Value of Derivative Liabilities		$ 0

[1] Includes basis.

[2] Represents market prices beyond defined terms for Levels 1 and 2.

[3] Averages weighted by volume.

[4] Represents volatilities unrepresented in published markets.

[5] Includes basis.

[6] Represents market prices beyond defined terms for Levels 1 and 2.

[7] Averages weighted by volume.

[8] Represents volatilities unrepresented in published markets.