Significant Financing Transactions - (Commercial Paper, Bank Loans and Letters of Credit Outstanding) (Details) (USD $)	Mar. 31, 2013
Line of Credit Facility [Line Items]
Facility Limit	$ 3,500,000,000
Outstanding Commercial Paper	2,003,000,000
Outstanding Letters of Credit	19,000,000
Facility Capacity Available	1,478,000,000
Virginia Electric and Power Company
Line of Credit Facility [Line Items]
Facility Limit	1,250,000,000
Outstanding Commercial Paper	661,000,000
Outstanding Letters of Credit	2,000,000
Facility Capacity Available	587,000,000
Credit Facility 1.5 Billion
Line of Credit Facility [Line Items]
Facility Limit	3,000,000,000	[1]
Outstanding Commercial Paper	2,003,000,000	[1]
Outstanding Letters of Credit	0	[1]
Facility Capacity Available	997,000,000	[1]
Credit Facility, to support letters of credit	1,500,000,000.0
Credit Facility 1.5 Billion | Virginia Electric and Power Company
Line of Credit Facility [Line Items]
Facility Limit	1,000,000,000	[2]
Outstanding Commercial Paper	661,000,000	[2]
Outstanding Letters of Credit	0	[2]
Facility Capacity Available	339,000,000	[2]
Credit Facility, to support letters of credit	1,500,000,000.0
Credit Facility 500 Million
Line of Credit Facility [Line Items]
Facility Limit	500,000,000	[3]
Outstanding Commercial Paper	0	[3]
Outstanding Letters of Credit	19,000,000	[3]
Facility Capacity Available	481,000,000	[3]
Amount of extended capacity for credit facility	400,000,000
Remaining amount of capacity of credit facility	100,000,000
Credit Facility 500 Million | Virginia Electric and Power Company
Line of Credit Facility [Line Items]
Facility Limit	250,000,000	[4]
Outstanding Commercial Paper	0	[4]
Outstanding Letters of Credit	2,000,000	[4]
Facility Capacity Available	$ 248,000,000	[4]

[1] This credit facility has a maturity date of September 2017, and 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.

[2] This credit facility has a maturity date of September 2017, and can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.5 billion (or the sub-limit, whichever is less) of letters of credit. Virginia Power's current sub-limit under this credit facility can be increased or decreased multiple times per year.

[3] The maturity date for $400 million of the $500 million in committed capacity of this credit facility is September 2017. The remaining $100 million has a maturity date of September 2016. This credit facility can be used to support bank borrowings, commercial paper and letter of credit issuances.

[4] The maturity date for $400 million of the $500 million in committed capacity of this credit facility is September 2017. The remaining $100 million has 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.