Derivatives and Hedge Accounting Activities (Volume of Derivative Activity) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013
Current Derivative Contract
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate	$ 1,750
Current Derivative Contract | Natural Gas | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	222,000,000,000	[1]
Current Derivative Contract | Natural Gas | Basis
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	723,000,000,000
Current Derivative Contract | Electricity | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	20,165,120	[1]
Current Derivative Contract | Electricity | Financial Transmission Rights
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	91,445,833
Current Derivative Contract | Capacity
Derivative Instruments, Gain (Loss) [Line Items]
Capacity (MW)	217,575
Current Derivative Contract | Liquids
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	158,508,000	[2]
Noncurrent Derivative Contract
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate	1,350
Noncurrent Derivative Contract | Natural Gas | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	38,000,000,000	[1]
Noncurrent Derivative Contract | Natural Gas | Basis
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	459,000,000,000
Noncurrent Derivative Contract | Electricity | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	14,488,783	[1]
Noncurrent Derivative Contract | Electricity | Financial Transmission Rights
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	459,947
Noncurrent Derivative Contract | Capacity
Derivative Instruments, Gain (Loss) [Line Items]
Capacity (MW)	48,886
Noncurrent Derivative Contract | Liquids
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	72,912,000	[2]
Virginia Electric and Power Company | Current Derivative Contract
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate	900
Virginia Electric and Power Company | Current Derivative Contract | Natural Gas | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	18,000,000,000
Virginia Electric and Power Company | Current Derivative Contract | Natural Gas | Basis
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	9,000,000,000
Virginia Electric and Power Company | Current Derivative Contract | Electricity | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	491,200
Virginia Electric and Power Company | Current Derivative Contract | Electricity | Financial Transmission Rights
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	89,107,999
Virginia Electric and Power Company | Current Derivative Contract | Capacity
Derivative Instruments, Gain (Loss) [Line Items]
Capacity (MW)	167,500
Virginia Electric and Power Company | Noncurrent Derivative Contract
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate	$ 0
Virginia Electric and Power Company | Noncurrent Derivative Contract | Natural Gas | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	0
Virginia Electric and Power Company | Noncurrent Derivative Contract | Natural Gas | Basis
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	0
Virginia Electric and Power Company | Noncurrent Derivative Contract | Electricity | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	0
Virginia Electric and Power Company | Noncurrent Derivative Contract | Electricity | Financial Transmission Rights
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	0
Virginia Electric and Power Company | Noncurrent Derivative Contract | Capacity
Derivative Instruments, Gain (Loss) [Line Items]
Capacity (MW)	18,300

[1] Includes options.

[2] Includes NGLs and oil.