Derivatives and Hedge Accounting Activities (Volume of Derivative Activity) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013
Current Derivative Contract
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate	$ 2,400
Current Derivative Contract | Natural Gas | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	149,000,000,000	[1]
Current Derivative Contract | Natural Gas | Basis
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	529,000,000,000
Current Derivative Contract | Electricity | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	17,059,889	[1]
Current Derivative Contract | Electricity | Financial Transmission Rights
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	64,859,720
Current Derivative Contract | Capacity
Derivative Instruments, Gain (Loss) [Line Items]
Capacity (MW)	133,650
Current Derivative Contract | Liquids
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	152,418,000	[2]
Noncurrent Derivative Contract
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate	1,150
Noncurrent Derivative Contract | Natural Gas | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	27,000,000,000	[1]
Noncurrent Derivative Contract | Natural Gas | Basis
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	379,000,000,000
Noncurrent Derivative Contract | Electricity | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	15,411,998	[1]
Noncurrent Derivative Contract | Electricity | Financial Transmission Rights
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	689,289
Noncurrent Derivative Contract | Capacity
Derivative Instruments, Gain (Loss) [Line Items]
Capacity (MW)	18,300
Noncurrent Derivative Contract | Liquids
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	35,700,000	[2]
Virginia Electric and Power Company | Current Derivative Contract
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate	600
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)	9,000,000,000
Virginia Electric and Power Company | Current Derivative Contract | Natural Gas | Basis
Derivative Instruments, Gain (Loss) [Line Items]
Volume of natural gas (cf)/ liquids (gallons)	5,000,000,000
Virginia Electric and Power Company | Current Derivative Contract | Electricity | Fixed Price
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	511,200
Virginia Electric and Power Company | Current Derivative Contract | Electricity | Financial Transmission Rights
Derivative Instruments, Gain (Loss) [Line Items]
Volume of electricity (MWh)	63,408,139
Virginia Electric and Power Company | Current Derivative Contract | Capacity
Derivative Instruments, Gain (Loss) [Line Items]
Capacity (MW)	121,500
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.