Organization and Basis of Presentation (Details Textuals) mi in Thousands, customer in Millions, $ in Millions			3 Months Ended	12 Months Ended
	Oct. 09, 2013 USD ($) MW	Jul. 08, 2013 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2015 USD ($) customer transmission_center company mi MW	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Regulatory Assets [Line Items]
Length of transmission lines | mi				24
Number of regional transmission centers | transmission_center				2
Regulatory assets that do not earn a current return				$ 148.0	$ 488.0
Net regulatory liabilities				116.0	243.0
Cost of nuclear fuel				418.0
Capitalized financing costs				49.0	49.0	$ 28.0
Interest costs capitalized				68.0	69.0	75.0
Net plant in service				34,792.0	33,334.0
Impairments of long-lived assets		$ (473.0)		(42.0)	0.0	(795.0)
Goodwill			$ 6,418.0	6,418.0	6,418.0	6,418.0
Other than temporary impairments				$ 102.0	37.0	90.0
Aggregate amount of capacity (in MWs) | MW				17,000
Ownership interest (percent)				3.00%
Deferred Tax Assets, Net, Noncurrent				$ 6,773.0	6,539.0
Deferred Tax Liabilities, Net, Noncurrent				$ 6,773.0	6,539.0
New Accounting Pronouncement, Early Adoption, Effect [Member]
Regulatory Assets [Line Items]
Deferred Tax Assets, Net, Noncurrent					518.0
Deferred Tax Liabilities, Net, Noncurrent					(518.0)
Bath County, Virginia
Regulatory Assets [Line Items]
Plant generation capacity | MW				3,003
Non-core [Member]
Regulatory Assets [Line Items]
Impairments of long-lived assets				$ (42.0)
Inventories
Regulatory Assets [Line Items]
Impairments of long-lived assets		$ (13.0)
Regulated Distribution
Regulatory Assets [Line Items]
Number of existing utility operating companies | company				10
Number of customers served by utility operating companies | customer				6
Property, plant and equipment, net				$ 2,000.0
Plant generation capacity | MW	3,790
Net plant in service				17,495.0	17,214.0
Goodwill			5,092.0	5,092.0	5,092.0	5,092.0
Regulated Distribution | Non-core [Member]
Regulatory Assets [Line Items]
Impairments of long-lived assets				$ (8.0)
Competitive Energy Services
Regulatory Assets [Line Items]
Plant generation capacity | MW				13,162
Net plant in service				$ 11,001.0	10,844.0
Goodwill			800.0	$ 800.0	800.0	800.0
Percentage of fair value in excess of carrying amount				10.00%
Competitive Energy Services | Non-core [Member]
Regulatory Assets [Line Items]
Impairments of long-lived assets				$ (34.0)
AE Supply
Regulatory Assets [Line Items]
Percent of ownership interest acquired	8.00%
Value of interest acquired	$ 73.0
Cash consideration received in asset swap transaction			$ 1,100.0
Assumption of pollution control note	$ 73.5
MP
Regulatory Assets [Line Items]
Percent of ownership interest acquired	80.00%
Value of interest acquired	$ 1,200.0
Impairments of long-lived assets						(322.0)
Regulatory liability						23.0
AGC | Bath County, Virginia
Regulatory Assets [Line Items]
Pumped storage hydroelectric station ownership percentage				40.00%
Plant generation capacity | MW				1,200
Net plant in service				$ 666.0
AGC | Competitive Energy Services
Regulatory Assets [Line Items]
Net plant in service				$ 484.0
Virginia Electric and Power Company | Bath County, Virginia
Regulatory Assets [Line Items]
Pumped storage hydroelectric station ownership percentage				60.00%
FES
Regulatory Assets [Line Items]
Net plant in service				$ 8,546.0	8,388.0
Goodwill				23.0	23.0
Other than temporary impairments				90.0	33.0	$ 79.0
Deferred Tax Assets, Net, Noncurrent				600.0	484.0
Deferred Tax Liabilities, Net, Noncurrent				$ 600.0	484.0
FES | New Accounting Pronouncement, Early Adoption, Effect [Member]
Regulatory Assets [Line Items]
Deferred Tax Assets, Net, Noncurrent					27.0
Deferred Tax Liabilities, Net, Noncurrent					$ (27.0)
Income Approach Valuation Technique | Goodwill [Member] | Competitive Energy Services
Regulatory Assets [Line Items]
Discount rate				8.25%
Fair Value Inputs, Earnings before Interest, Taxes, Depreciation, and Amortization Multiple				7.0
Signal Peak | Global Holding | FEV
Regulatory Assets [Line Items]
Impairments of long-lived assets				$ (362.0)
Ownership interest (percent)				33.33%
Deferred Charges and Other Assets [Member] | New Accounting Pronouncement, Early Adoption, Effect [Member]
Regulatory Assets [Line Items]
Deferred Finance Costs, Net				$ (93.0)
Deferred Charges and Other Assets [Member] | FES | New Accounting Pronouncement, Early Adoption, Effect [Member]
Regulatory Assets [Line Items]
Deferred Finance Costs, Net				$ (17.0)