Significant Financing Transactions - (Commercial Paper, Bank Loans and Letters of Credit Outstanding) (Details) (USD $)	Sep. 30, 2012
Facility Limit	$ 3,500,000,000
Outstanding Commercial Paper	1,382,000,000
Outstanding Letters of Credit	23,000,000
Facility Capacity Available	2,095,000,000
Three Year Joint Revolving Credit Facility
Facility Limit	500,000,000	[1],[2]
Outstanding Commercial Paper	0	[1]
Outstanding Letters of Credit	23,000,000	[1]
Facility Capacity Available	477,000,000	[1]
Amount of extended capacity for credit facility	400,000,000
Remaining amount of capacity of credit facility	100,000,000
Credit Facility 1.5 Billion | Three Year Joint Revolving Credit Facility
Facility Limit	3,000,000,000	[3]
Outstanding Commercial Paper	1,382,000,000	[3]
Outstanding Letters of Credit	0	[3]
Facility Capacity Available	1,618,000,000	[3]
Credit Facility, to support letters of credit	1,500,000,000
Virginia Electric and Power Company
Facility Limit	1,250,000,000
Outstanding Commercial Paper	105,000,000
Outstanding Letters of Credit	2,000,000
Facility Capacity Available	1,143,000,000
Virginia Electric and Power Company | Three Year Joint Revolving Credit Facility
Facility Limit	250,000,000	[2]
Outstanding Commercial Paper	0	[2]
Outstanding Letters of Credit	2,000,000	[2]
Facility Capacity Available	248,000,000	[2]
Virginia Electric and Power Company | Credit Facility 1.5 Billion | Three Year Joint Revolving Credit Facility
Facility Limit	1,000,000,000	[3]
Outstanding Commercial Paper	105,000,000	[3]
Outstanding Letters of Credit	0	[3]
Facility Capacity Available	895,000,000	[3]
Credit Facility, to support letters of credit	$ 1,500,000,000

[1] Effective September 2012, the maturity date for $400 million of the $500 million in committed capacity of this credit facility was extended from September 2016 to September 2017. The remaining $100 million continues to have a maturity date of September 2016. This credit facility can be used to support bank borrowings, commercial paper and letter of credit issuances.

[2] Effective September 2012, the maturity date for $400 million of the $500 million in committed capacity of this credit facility was extended from September 2016 to September 2017. The remaining $100 million continues to have a maturity date of September 2016. This credit facility can be used to support bank borrowings, commercial paper and letter of credit issuances. Virginia Power's current sub-limit under this credit facility can be increased or decreased multiple times per year.

[3] Effective September 2012, the maturity date was extended from September 2016 to September 2017. This credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.5 billion of letters of credit.