Derivatives and Hedge Accounting Activities (Volume of Derivative Activity) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Current Derivative Contract
Interest rate	$ 1,350
Current Derivative Contract | Natural Gas | Fixed Price
Volume of natural gas (cf)/ liquids (gallons)	292,000,000,000	[1]
Current Derivative Contract | Natural Gas | Basis
Volume of natural gas (cf)/ liquids (gallons)	875,000,000,000
Current Derivative Contract | Electricity | Fixed Price
Volume of electricity (MWh)	19,932,885	[1]
Current Derivative Contract | Electricity | Financial Transmission Rights
Volume of electricity (MWh)	19,950,674
Current Derivative Contract | Capacity
Capacity (MW)	200,525
Current Derivative Contract | Liquids
Volume of natural gas (cf)/ liquids (gallons)	161,322,000	[2]
Noncurrent Derivative Contract
Interest rate	1,650
Noncurrent Derivative Contract | Natural Gas | Fixed Price
Volume of natural gas (cf)/ liquids (gallons)	47,000,000,000	[1]
Noncurrent Derivative Contract | Natural Gas | Basis
Volume of natural gas (cf)/ liquids (gallons)	482,000,000,000
Noncurrent Derivative Contract | Electricity | Fixed Price
Volume of electricity (MWh)	15,662,175	[1]
Noncurrent Derivative Contract | Electricity | Financial Transmission Rights
Volume of electricity (MWh)	0
Noncurrent Derivative Contract | Capacity
Capacity (MW)	90,744
Noncurrent Derivative Contract | Liquids
Volume of natural gas (cf)/ liquids (gallons)	109,284,000	[2]
Virginia Electric and Power Company | Current Derivative Contract
Interest rate	0
Virginia Electric and Power Company | Current Derivative Contract | Natural Gas | Fixed Price
Volume of natural gas (cf)/ liquids (gallons)	16,000,000,000
Virginia Electric and Power Company | Current Derivative Contract | Natural Gas | Basis
Volume of natural gas (cf)/ liquids (gallons)	8,000,000,000
Virginia Electric and Power Company | Current Derivative Contract | Electricity | Fixed Price
Volume of electricity (MWh)	644,000
Virginia Electric and Power Company | Current Derivative Contract | Electricity | Financial Transmission Rights
Volume of electricity (MWh)	17,168,056
Virginia Electric and Power Company | Current Derivative Contract | Capacity
Capacity (MW)	152,000
Virginia Electric and Power Company | Noncurrent Derivative Contract
Interest rate	$ 250
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)	48,800

[1] Includes options.

[2] Includes NGLs and oil.