Derivatives and Hedge Accounting Activities (Volume of Derivative Activity) (Details) (USD $)	Sep. 30, 2012
Current Derivative Contract
Interest rate	$ 1,900,000,000
Current Derivative Contract | Natural Gas | Fixed Price
Volume of natural gas (cf)/ liquids (gallons)	253,000,000,000	[1]
Current Derivative Contract | Natural Gas | Basis
Volume of natural gas (cf)/ liquids (gallons)	820,000,000,000	[1]
Current Derivative Contract | Electricity | Fixed Price
Volume of electricity (MWh)	21,889,805	[1]
Current Derivative Contract | Electricity | Financial Transmission Rights
Volume of electricity (MWh)	71,103,622
Current Derivative Contract | Capacity
Capacity (MW)	100,425
Current Derivative Contract | Liquids
Volume of natural gas (cf)/ liquids (gallons)	140,658,000	[2]
Noncurrent Derivative Contract
Interest rate	2,340,000,000
Noncurrent Derivative Contract | Natural Gas | Fixed Price
Volume of natural gas (cf)/ liquids (gallons)	74,000,000,000	[1]
Noncurrent Derivative Contract | Natural Gas | Basis
Volume of natural gas (cf)/ liquids (gallons)	500,000,000,000	[1]
Noncurrent Derivative Contract | Electricity | Fixed Price
Volume of electricity (MWh)	15,308,096	[1]
Noncurrent Derivative Contract | Electricity | Financial Transmission Rights
Volume of electricity (MWh)	237,523
Noncurrent Derivative Contract | Capacity
Capacity (MW)	207,460
Noncurrent Derivative Contract | Liquids
Volume of natural gas (cf)/ liquids (gallons)	168,210,000	[2]
Virginia Electric and Power Company | Current Derivative Contract
Interest rate	900,000,000
Virginia Electric and Power Company | Current Derivative Contract | Natural Gas | Fixed Price
Volume of natural gas (cf)/ liquids (gallons)	12,000,000,000
Virginia Electric and Power Company | Current Derivative Contract | Natural Gas | Basis
Volume of natural gas (cf)/ liquids (gallons)	6,000,000,000
Virginia Electric and Power Company | Current Derivative Contract | Electricity | Fixed Price
Volume of electricity (MWh)	564,800
Virginia Electric and Power Company | Current Derivative Contract | Electricity | Financial Transmission Rights
Volume of electricity (MWh)	69,715,081
Virginia Electric and Power Company | Current Derivative Contract | Capacity
Capacity (MW)	61,000
Virginia Electric and Power Company | Noncurrent Derivative Contract
Interest rate	$ 340,000,000
Virginia Electric and Power Company | Noncurrent Derivative Contract | Natural Gas | Fixed Price
Volume of natural gas (cf)/ liquids (gallons)	0
Virginia Electric and Power Company | Noncurrent Derivative Contract | Natural Gas | Basis
Volume of natural gas (cf)/ liquids (gallons)	0
Virginia Electric and Power Company | Noncurrent Derivative Contract | Electricity | Fixed Price
Volume of electricity (MWh)	0
Virginia Electric and Power Company | Noncurrent Derivative Contract | Electricity | Financial Transmission Rights
Volume of electricity (MWh)	0
Virginia Electric and Power Company | Noncurrent Derivative Contract | Capacity
Capacity (MW)	139,800

[1] Includes options.

[2] Includes NGLs and oil.