Long-Term Debt (Narrative) (Details)								1 Months Ended									12 Months Ended
	Oct. 01, 2024	Aug. 15, 2016 USD ($) shares		Jul. 01, 2016 shares	Jun. 30, 2016	Apr. 01, 2016 shares	Jul. 01, 2014 USD ($) shares	Jul. 31, 2017 shares	Aug. 31, 2016 USD ($)	Jul. 31, 2016 USD ($) shares	Apr. 30, 2016 shares	Dec. 31, 2014 USD ($)	Oct. 31, 2014 USD ($)	Jul. 31, 2014 USD ($)	Jun. 30, 2013 USD ($)	Sep. 30, 2011	Dec. 31, 2016 USD ($) senior_note $ / shares shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jan. 31, 2017 USD ($)	Jun. 29, 2016	May 31, 2016 USD ($)	Mar. 31, 2016 USD ($)	Nov. 30, 2014 USD ($)	Jun. 30, 2009 USD ($)	Sep. 30, 2006 USD ($)	Jun. 30, 2006 USD ($)
Debt Instrument [Line Items]
Aggregate outstanding principal amount																	$ 32,192,000,000
Make-whole premium amount																	$ 0	$ 0	$ 284,000,000
Period of deferral													10 years
Period for consideration of proceeds (days)																180 days	365 days
Interest in RSN issued by Dominion (percentage)																	5.00%
Minimum
Debt Instrument [Line Items]
Shares to be issued under purchase contracts | shares											11,600,000
Maximum
Debt Instrument [Line Items]
Shares to be issued under purchase contracts | shares											14,500,000
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
Common Stock
Debt Instrument [Line Items]
Purchase price to be paid under stock purchase contracts (in dollars per unit) | $ / shares																	$ 50
Shares reserved and available for issuance | shares																	40,900,000
Capital Unit, Class A
Debt Instrument [Line Items]
Issuance of Dominion Midstream common units, net of offering costs									$ 1,400,000,000.0					$ 1,000,000,000	$ 550,000,000
Payment percentage rate on Equity Units							6.375%		6.75%						6.125%
Purchase price to be paid under stock purchase contracts (in dollars per unit) | $ / shares																	$ 50
Number of shares issued | shares		28,000,000	[1]				20,000,000
Capital Unit, Class B
Debt Instrument [Line Items]
Issuance of Dominion Midstream common units, net of offering costs															$ 550,000,000
Payment percentage rate on Equity Units															6.00%
Remarketable Subordinated Notes | Capital Unit, Class A
Debt Instrument [Line Items]
Principal amount of notes		$ 1,400,000,000.0	[1]				$ 1,000,000,000																$ 550,000,000
Interest rate (percentage)		2.00%	[1],[2]				1.50%																1.07%
Number of shares issued | shares				8,500,000.0		8,500,000.0				8,500,000.0	8,500,000.0
Remarketable Subordinated Notes | Capital Unit, Class B
Debt Instrument [Line Items]
Principal amount of notes																						$ 550,000,000
Interest rate (percentage)																						1.18%
Remarketable Subordinated Notes, 2014 Series A, due July 1, 2020
Debt Instrument [Line Items]
Interest in RSN issued by Dominion (percentage)																	5.00%
Remarketable Subordinated Notes, 2016 Series A-1, due August 15, 2021
Debt Instrument [Line Items]
Interest in RSN issued by Dominion (percentage)																	2.50%
Remarketable Subordinated Notes, 2016 Series A-1, due August 15, 2021 | Capital Unit, Class A
Debt Instrument [Line Items]
Principal amount of notes		$ 700,000,000
Remarketable Subordinated Notes, 2016 Series A-2, due August 15, 2024
Debt Instrument [Line Items]
Interest in RSN issued by Dominion (percentage)																	2.50%
Remarketable Subordinated Notes, 2016 Series A-2, due August 15, 2024 | Capital Unit, Class A
Debt Instrument [Line Items]
Principal amount of notes		$ 700,000,000
June 2006 hybrids
Debt Instrument [Line Items]
Interest rate (percentage)																					7.50%
Aggregate redemption price paid																		14,000,000					$ 38,000,000
Junior subordinated notes																											$ 300,000,000
June 2006 hybrids | LIBOR
Debt Instrument [Line Items]
Spread on variable percentage rate					2.825%
September 2006 hybrids
Debt Instrument [Line Items]
Interest rate (percentage)																2.30%
Aggregate redemption price paid																		$ 3,000,000					$ 4,000,000
Junior subordinated notes																										$ 500,000,000
June 2009 hybrids
Debt Instrument [Line Items]
Interest rate (percentage)																									8.375%
Aggregate redemption price paid													$ 685,000,000
Junior subordinated notes																									$ 685,000,000
Senior Notes
Debt Instrument [Line Items]
Number of outstanding series of senior notes | senior_note																	5
Aggregate outstanding principal amount																	$ 1,900,000,000
Aggregate redemption price paid																	2,200,000,000
Make-whole premium amount												$ 263,000,000
Interest charges												284,000,000
Senior Notes | Senior Notes, Due in 2019 | Subsequent Event
Debt Instrument [Line Items]
Principal amount of notes																				$ 400,000,000
Interest rate (percentage)																				1.875%
Senior Notes | Senior Notes, Due in 2022 | Subsequent Event
Debt Instrument [Line Items]
Principal amount of notes																				$ 400,000,000
Interest rate (percentage)																				2.75%
Convertible Debt
Debt Instrument [Line Items]
Outstanding contingent convertible senior notes																								$ 22,000,000
Shares issued in excess of principal amounts related to converted securities												$ 26,000,000
Unsecured Junior Subordinated Notes
Debt Instrument [Line Items]
Aggregate outstanding principal amount																	$ 1,100,000,000
Unsecured Junior Subordinated Notes | Enhanced Junior Subordinated Notes, 5.75%
Debt Instrument [Line Items]
Principal amount of notes													$ 685,000,000
Interest rate (percentage)													5.75%
Unsecured Junior Subordinated Notes | Enhanced Junior Subordinated Notes, 5.75% | LIBOR | Scenario, Forecast
Debt Instrument [Line Items]
Spread on variable percentage rate	3.057%
Unsecured Junior Subordinated Notes | June 2006 and September 2006 hybrids | Maximum
Debt Instrument [Line Items]
Amount purchased and cancelled										$ 200,000,000
Unsecured Junior Subordinated Notes | June 2006 hybrids
Debt Instrument [Line Items]
Amount purchased and cancelled										125,000,000
Unsecured Junior Subordinated Notes | September 2006 hybrids
Debt Instrument [Line Items]
Amount purchased and cancelled										74,000,000
Unsecured Junior Subordinated Notes | July 2016 Hybrids
Debt Instrument [Line Items]
Principal amount of notes										$ 800,000,000
Interest rate (percentage)										5.25%
Unsecured Junior Subordinated Notes | Series A Junior Subordinated Notes
Debt Instrument [Line Items]
Interest rate (percentage)																							4.104%
Unsecured Junior Subordinated Notes | Series B Junior Subordinated Notes
Debt Instrument [Line Items]
Interest rate (percentage)																						2.962%

[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.