Significant Financing Transactions (Narrative) (Details)					1 Months Ended						9 Months Ended
		Aug. 15, 2016 USD ($) shares	Jul. 01, 2016 shares	Apr. 01, 2016 shares	Aug. 31, 2019 shares	Nov. 30, 2016 USD ($)	Aug. 31, 2016 USD ($)	Jul. 31, 2016 USD ($) shares	Apr. 30, 2016 USD ($) shares	Dec. 31, 2014 USD ($) agreement	Sep. 30, 2016 USD ($) facility $ / shares shares	Sep. 30, 2015 USD ($)	Oct. 31, 2016 USD ($)	Oct. 01, 2016 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2016 EUR (€)	May 31, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jun. 30, 2015 USD ($)
Debt Instrument [Line Items]
Amount issued for 2016 Series A Equity Units											$ 2,079,000,000
Issuance of common stock											$ 2,079,000,000	$ 717,000,000
Shelf Registration for Sale of Common Stock through At-the-market Program
Debt Instrument [Line Items]
Number of sales agency agreements | agreement										4
Common stock reserved for issuance in connection with stock purchase contracts (up to $200 million)																			$ 200,000,000
Underwritten Public Offering
Debt Instrument [Line Items]
Number of common units issued | shares									10,200,000
Issuance of common stock									$ 756,000,000
Maximum | Shelf Registration for Sale of Common Stock through At-the-market Program
Debt Instrument [Line Items]
Aggregate amount of common stock in which the company may offer under SEC shelf registration (up to $500 million)										$ 500,000,000
Common Stock
Debt Instrument [Line Items]
Shares of common stock reserved for issuance with stock purchase contracts | shares											23,100,000
Scenario, Forecast | Minimum
Debt Instrument [Line Items]
Shares to be issued under purchase contracts | shares					15,000,000
Scenario, Forecast | Maximum
Debt Instrument [Line Items]
Shares to be issued under purchase contracts | shares					18,700,000
Series A RSNs
Debt Instrument [Line Items]
Units Issued | shares	[1]	28,000,000
Amount issued for 2016 Series A Equity Units							$ 1,400,000,000.0
Purchase price to be paid under stock purchase contracts (in dollars per corporate unit) | $ / shares											$ 50
Remarketable Subordinated Notes | Series A RSNs
Debt Instrument [Line Items]
Total Long-term Debt	[1]	$ 1,400,000,000.0
Interest rate percentage	[1],[2]	2.00%
Units Issued | shares			8,500,000.0	8,500,000.0				8,500,000.0	8,500,000.0
Remarketable Subordinated Notes, 2013 Series A, due 2021 | Series A RSNs
Debt Instrument [Line Items]
Total Long-term Debt																		$ 550,000,000
Interest rate percentage																		1.07%
Remarketable Subordinated Notes, 2013 Series B, due 2019 | Series B RSNs
Debt Instrument [Line Items]
Total Long-term Debt																	$ 550,000,000
Interest rate percentage																	1.18%
Remarketable Subordinated Notes, 2016 Series A-1, due 2021
Debt Instrument [Line Items]
Interest in RSNs issued by Dominion (percentage)											2.50%
Remarketable Subordinated Notes, 2016 Series A-1, due 2021 | Series A RSNs
Debt Instrument [Line Items]
Total Long-term Debt		$ 700,000,000
Remarketable Subordinated Notes, 2016 Series A-2, due 2024
Debt Instrument [Line Items]
Interest in RSNs issued by Dominion (percentage)											2.50%
Remarketable Subordinated Notes, 2016 Series A-2, due 2024 | Series A RSNs
Debt Instrument [Line Items]
Total Long-term Debt		$ 700,000,000
Series A Junior Subordinated Notes | Enhanced Junior Subordinated Notes
Debt Instrument [Line Items]
Interest rate percentage																		4.104%
Series B Junior Subordinated Notes | Enhanced Junior Subordinated Notes
Debt Instrument [Line Items]
Interest rate percentage																	2.962%
June 2006 and September 2006 hybrids | Maximum | Enhanced Junior Subordinated Notes
Debt Instrument [Line Items]
Amount purchased and cancelled								$ 200,000,000
June 2006 hybrids | Enhanced Junior Subordinated Notes
Debt Instrument [Line Items]
Amount purchased and cancelled								125,000,000										$ 38,000,000
September 2006 hybrids | Enhanced Junior Subordinated Notes
Debt Instrument [Line Items]
Amount purchased and cancelled								74,000,000										$ 4,000,000
July 2016 Hybrids | Enhanced Junior Subordinated Notes
Debt Instrument [Line Items]
Total Long-term Debt								$ 800,000,000
Interest rate percentage								5.25%
1.60% Senior Notes Due in 2019 | Senior Notes
Debt Instrument [Line Items]
Total Long-term Debt															$ 500,000,000
Interest rate percentage															1.60%	1.60%
2.0% Senior Notes Due in 2021 | Senior Notes
Debt Instrument [Line Items]
Total Long-term Debt															$ 400,000,000
Interest rate percentage															2.00%	2.00%
2.85% Senior Notes Due in 2026 | Senior Notes
Debt Instrument [Line Items]
Total Long-term Debt															$ 400,000,000
Interest rate percentage															2.85%	2.85%
1.50% Senior Notes Due in 2018 | Senior Notes
Debt Instrument [Line Items]
Total Long-term Debt											$ 300,000,000
Interest rate percentage											1.50%
Private Placement Term Loan Agreement Maturing in September 2017 | Term loan agreement
Debt Instrument [Line Items]
Total Long-term Debt											$ 1,200,000,000.0
Private Placement Term Loan Agreement Maturing in September 2017 | Term loan agreement | Long-term Debt
Debt Instrument [Line Items]
Borrowings under private placement term loan included in long term debt											$ 348,000,000
Virginia Electric and Power Company
Debt Instrument [Line Items]
Number of joint revolving credit facilities | facility											2
Credit facility											$ 120,000,000
Virginia Electric and Power Company | Subsequent Event
Debt Instrument [Line Items]
Credit facility													$ 100,000,000	$ 120,000,000
Virginia Electric and Power Company | Tax Exempt Debt
Debt Instrument [Line Items]
Variable rate tax-exempt financings											$ 100,000,000
Dominion Gas Holdings, LLC
Debt Instrument [Line Items]
Number of joint revolving credit facilities | facility											2
Dominion Gas Holdings, LLC | 3.8% Senior Notes Due in 2031 | Senior Notes
Debt Instrument [Line Items]
Total Long-term Debt																	$ 150,000,000
Interest rate percentage																	3.80%
Dominion Gas Holdings, LLC | 2.875% Senior Notes Due in 2023 | Senior Notes
Debt Instrument [Line Items]
Total Long-term Debt															$ 250,000,000
Interest rate percentage															2.875%	2.875%
Dominion Gas Holdings, LLC | 1.45% Senior Notes Due in 2026 | Senior Notes
Debt Instrument [Line Items]
Total Long-term Debt | €																€ 250,000,000
Interest rate percentage															1.45%	1.45%
Dominion Gas Holdings, LLC | 1.45% Senior Notes Due in 2026 | Senior Notes | Long-term Debt
Debt Instrument [Line Items]
Total Long-term Debt															$ 280,000,000
Amount of senior notes at period end											$ 281,000,000
Dominion Midstream Partners, LP | Subsequent Event | Scenario, Forecast | Underwritten Public Offering | Limited Partner
Debt Instrument [Line Items]
Net proceeds from issuance and public offering of common units						$ 348,000,000

[1] The maturity dates of the $700 million Series A-1 RSNs and $700 million Series A-2 RSNs are August 15, 2021 and August 15, 2024, respectively.

[2] Annual interest rate applies to each of the Series A-1 RSNs and Series A-2 RSNs.