Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2017	Sep. 30, 2016	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Actual return (loss) on plan assets				$ 534	$ (72)
Expected return on pension and other postretirement plan assets				691	648
Net actuarial loss					25
Accumulated benefit obligation				7,300	5,800
Estimated reduction in net cumulative required contributions				$ 200
Cumulative required contribution period (years)				10 years
Expected contribution to voluntary employees beneficiary association				$ 12
Amounts recognized in employer matching contributions				44	43	$ 41
Organizational Design Initiative | Special Termination Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Organizational design initiative charges				65
Organizational design initiative charges, after tax				$ 40
Common and preferred stocks
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined benefit plan, actual plan asset allocation percentages				28.00%
Government securities
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined benefit plan, actual plan asset allocation percentages				18.00%
Fixed Income
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined benefit plan, actual plan asset allocation percentages				35.00%
Real estate funds
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined benefit plan, actual plan asset allocation percentages				3.00%
Other alternative investments
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined benefit plan, actual plan asset allocation percentages				16.00%
Capital Contribution to Dominion Questar to Fund Pension Contributions | Dominion Questar Corporation | Subsequent Event
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Capital contribution to Dominion Questar	$ 75
Collective Bargaining Agreement
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Period for experience study of employee demographics				5 years
Increase in net periodic benefit costs for 2017				$ 42
Dominion Gas Holdings, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Actual return (loss) on plan assets				130	(13)
Expected return on pension and other postretirement plan assets				157	150
Net actuarial loss					3
Accumulated benefit obligation				640	578
Amounts recognized in employer matching contributions				7	7	7
Dominion Gas Holdings, LLC | Organizational Design Initiative | Special Termination Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Organizational design initiative charges				8
Organizational design initiative charges, after tax				5
Dominion Gas Holdings, LLC | Dominion Retiree Health And Welfare Plan | Multiemployer Plans, Postretirement Benefit | Other operations and maintenance expense
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Net periodic benefit cost				(4)	(5)	(5)
Virginia Electric and Power Company
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Amounts recognized in employer matching contributions				19	18	17
Virginia Electric and Power Company | Organizational Design Initiative | Special Termination Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Organizational design initiative charges				33
Organizational design initiative charges, after tax				20
Virginia Electric and Power Company | Other operations and maintenance expense
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Net periodic benefit cost				79	97	75
Virginia Electric and Power Company | Dominion Retiree Health And Welfare Plan | Other operations and maintenance expense
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Net periodic benefit cost				(29)	(16)	(18)
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Actual return (loss) on plan assets				426	(71)
Expected return on pension and other postretirement plan assets				573	531	$ 499
Net actuarial loss				(161)
Actuarial (gains) losses during the year				$ 784	$ (443)
Discount rate (percentage)					4.40%
Expected long-term rate of return on plan assets (percentage)				8.75%	8.75%	8.75%
Net periodic benefit cost				$ (25)	$ 44	$ 20
Pension Benefits | Collective Bargaining Agreement
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Actuarial (gains) losses during the year				290
Pension Benefits | Dominion Gas Holdings, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Actual return (loss) on plan assets				107	(14)
Expected return on pension and other postretirement plan assets				134	126	$ 115
Net actuarial loss				(16)
Actuarial (gains) losses during the year				$ 64	$ (43)
Discount percentage rate used for remeasurement				4.50%	4.99%
Discount rate (percentage)				4.99%	4.40%	5.20%
Expected long-term rate of return on plan assets (percentage)				8.75%	8.75%	8.75%
Net periodic benefit cost				$ (78)	$ (63)	$ (55)
Pension Benefits | Dominion Gas Holdings, LLC | Other operations and maintenance expense
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Net periodic benefit cost				(45)	(38)	(37)
Pension Benefits | Dominion Gas Holdings, LLC | Collective Bargaining Agreement
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Actuarial (gains) losses during the year				24
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Actual return (loss) on plan assets				108	(1)
Expected return on pension and other postretirement plan assets				118	117	$ 111
Net actuarial loss				(13)
Actuarial (gains) losses during the year				$ 166	$ (138)
Discount rate (percentage)					4.40%
Expected long-term rate of return on plan assets (percentage)				8.50%	8.50%	8.50%
Net periodic benefit cost				$ (49)	$ (31)	$ (38)
Other Postretirement Benefits | Collective Bargaining Agreement
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Actuarial (gains) losses during the year				38
Other Postretirement Benefits | Dominion Gas Holdings, LLC
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Actual return (loss) on plan assets				23	1
Expected return on pension and other postretirement plan assets				23	24	$ 23
Net actuarial loss				(2)
Actuarial (gains) losses during the year				$ 28	$ (31)
Discount percentage rate used for remeasurement				4.47%	4.93%
Discount rate (percentage)				4.93%	4.40%
Expected long-term rate of return on plan assets (percentage)				8.50%	8.50%	8.50%
Net periodic benefit cost				$ (2)	$ (2)	$ (5)
Other Postretirement Benefits | Dominion Gas Holdings, LLC | Collective Bargaining Agreement
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Actuarial (gains) losses during the year				$ 9
Other Postretirement Benefits | East Ohio
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Retirement age			65 years
Increase (decrease) in accumulated postretirement benefit obligation due to amendment			$ 22
Increase (reduction) in net periodic benefit credit due to amendment (less than $1 million)			$ (1)
Discount rate (percentage)			4.20%
Expected long-term rate of return on plan assets (percentage)			8.50%
Retiree medical coverage
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Retirement age		65 years
Increase (decrease) in accumulated postretirement benefit obligation due to amendment		$ (37)
Increase (reduction) in net periodic benefit credit due to amendment (less than $1 million)		$ 9
Discount percentage rate used for remeasurement		3.71%