Regulatory Matters (Details) (USD $)	3 Months Ended	12 Months Ended			1 Months Ended	3 Months Ended	0 Months Ended	3 Months Ended		0 Months Ended			12 Months Ended	0 Months Ended					12 Months Ended	3 Months Ended	12 Months Ended	0 Months Ended						1 Months Ended
	Jun. 30, 2014	Dec. 31, 2014 entity	Dec. 31, 2013	Dec. 31, 2012	Apr. 30, 2007 kv	Mar. 31, 2014	Oct. 09, 2013	Dec. 31, 2013	Dec. 31, 2014	Aug. 24, 2012	Sep. 03, 2013	Dec. 22, 2011	Dec. 31, 2008	Mar. 19, 2014	Jan. 27, 2014	May 04, 2014	Aug. 07, 2013	Apr. 13, 2012	Dec. 31, 2009	Sep. 30, 2013	Dec. 31, 2010	Aug. 04, 2014	Feb. 03, 2015	Dec. 02, 2014	Aug. 29, 2014	Apr. 30, 2014	Nov. 03, 2014	Oct. 31, 2006 proceeding	Dec. 24, 2014 waiver filing	Aug. 31, 2011	Oct. 06, 2009	Feb. 22, 2013	Nov. 30, 2012	Jan. 08, 2015	Oct. 22, 2014	Feb. 24, 2014	Sep. 30, 2014	Feb. 06, 2013
Regulatory Matters [Line Items]
Interest coverage, amount outstanding		$ 1,000,000							$ 1,000,000
Amortization of regulatory asset, net		12,000,000	539,000,000	(68,000,000)
Asset Impairment Charges	473,000,000	0	795,000,000	0
Regional Enforcement Entities		8
FERC
Regulatory Matters [Line Items]
Power threshold for cost methodology					500
Denied Recovery Charges of Exit Fees		78,800,000							78,800,000
FERC | PJM Capacity
Regulatory Matters [Line Items]
Public Utilities, Number of Filings Submitted																													2
Public Utilities, Number of Waivers Filed																													1
FERC | PJM Capacity | Maximum
Regulatory Matters [Line Items]
Plant generation capacity																													2,000
PJM | FERC
Regulatory Matters [Line Items]
Compliance Filing, Hybrid Methodology, Beneficiary Pays Cost Allocation		50.00%							50.00%
Compliance Filing, Hybrid Methodology, Postage Stamp Cost Allocation		50.00%							50.00%
FES
Regulatory Matters [Line Items]
Equity contribution from parent		500,000,000	1,500,000,000	0		500,000,000
Loans to affiliated companies, net		0	276,000,000	107,000,000
AE Supply
Regulatory Matters [Line Items]
Cash consideration received in asset swap transaction								1,100,000,000
Assumption of pollution control note							73,500,000
MP
Regulatory Matters [Line Items]
Asset Impairment Charges									322,000,000
Regulatory liability									23,000,000
PATH | FERC
Regulatory Matters [Line Items]
Regulatory Asset, Cost Recovery, Proposed Return on Equity										10.90%
Base Return On Equity										10.40%
Return On Equity Granted For Regional Transmission Organization Participation										0.50%
Remaining Recovery Period of Regulatory Assets										5 years
PATH-Allegheny | FERC
Regulatory Matters [Line Items]
Cost recovery, PP&E reclassified to Regulatory Assets										62,000,000
Path-WV | FERC
Regulatory Matters [Line Items]
Cost recovery, PP&E reclassified to Regulatory Assets										59,000,000
FES and AE Supply | FERC | FTR Underfunding Complaint | Minimum
Regulatory Matters [Line Items]
Revenues Lost of Which the Entity is Entitled		94,000,000
MARYLAND
Regulatory Matters [Line Items]
Proposed electric consumption reduction percentage													10.00%
Proposed electric demand reduction percentage													15.00%
Expenditures for cost recovery program																														64,000,000	101,000,000
Recovery period for expenditures for cost recovery program		3 years										5 years
Maximum penalty assessed, in dollars per day per violation		25,000
Expected infrastructure investments											2,700,000,000
Expected infrastructure investments, period											15 years
NEW JERSEY
Regulatory Matters [Line Items]
Number of supply components		2							2
Number of BGS		1							1
Requested approval for increase in revenues																																603,000,000	31,000,000
NEW JERSEY | Subsequent Event
Regulatory Matters [Line Items]
Public Utilities, Recommended Annual Rate Decrease																																		107,500,000
NEW JERSEY | NJBPU
Regulatory Matters [Line Items]
Requested increase in revenues														580,000,000
NEW JERSEY | JCP&L | Rate Counsel
Regulatory Matters [Line Items]
Recommend Reduction in Base Rates for Electric Service															214,900,000
NEW JERSEY | JCP&L | NJBPU
Regulatory Matters [Line Items]
Disallowed recovery costs			8,000,000
Public Utilities, Requested Recovery of Deferred Costs, Allowed Amount																																				736,000,000
Public Utilities, Requested Recovery of Deferred Costs																																				744,000,000
Recommend Reduction in Base Rates for Electric Service															207,400,000
Public Utilities, Requested Revision of Debt Rate																5.93%
Public Utilities, Requested Rate Increase (Decrease), Amount																9,100,000
Allowed CTA Revenue Adjustment																																			5,000,000
OHIO
Regulatory Matters [Line Items]
Generation discount for low income customers		6.00%
Recovery Period		5 years
Costs avoided by customers		360,000,000
ESP Extension Term																		2 years
Generation supply auction period, after approval		3 years
Economic Development and Assistance Plan, Term		3 years
Proposed Purchase Power Agreement, Term		15 years
Annual revenue cap for rider																																					30,000,000
Generation supply auction period, before approval		1 year
Utilities required to reduce peak demand																			1.00%
Portfolio Plan, Estimated Cost		250,000,000							250,000,000
Portion of Revenue Obtained to be Received		20.00%
Credit to Non-Shopping Customers																	43,400,000
OHIO | Annually 2017 Through 2020
Regulatory Matters [Line Items]
Utilities required to additionally reduce peak demand		0.75%
OHIO | Year 2014
Regulatory Matters [Line Items]
Annual energy savings		2,237,000
OHIO | Annually Through 2018
Regulatory Matters [Line Items]
Utilities required to additionally reduce peak demand		0.75%
OHIO | PUCO
Regulatory Matters [Line Items]
Number of renewable energy auctions																	1
Amortization of regulatory asset, net								51,000,000
PENNSYLVANIA
Regulatory Matters [Line Items]
Marginal Transmission Refund Period		29 months
Marginal transmission losses																					254,000,000
Asset Impairment Charges																				254,000,000
Number of Requests For Proposal								1
Request for Proposal, Project Term								2 years
PENNSYLVANIA | Three Month Period
Regulatory Matters [Line Items]
Energy Contract, Term								3 months
PENNSYLVANIA | Twelve Month Period
Regulatory Matters [Line Items]
Energy Contract, Term								12 months
PENNSYLVANIA | Twenty-Four Month Period
Regulatory Matters [Line Items]
Energy Contract, Term								24 months
PENNSYLVANIA | Forty-Eight Month Period
Regulatory Matters [Line Items]
Energy Contract, Term								48 months
PENNSYLVANIA | Unfavorable Regulatory Action
Regulatory Matters [Line Items]
Statutory penalty, maximum																																						234,000,000
PENNSYLVANIA | ME
Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																						151,900,000
PENNSYLVANIA | ME | Subsequent Event
Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																							89,300,000
PENNSYLVANIA | PN
Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																						119,800,000
PENNSYLVANIA | PN | Subsequent Event
Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																							90,800,000
PENNSYLVANIA | Penn
Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																						28,500,000
PENNSYLVANIA | Penn | Subsequent Event
Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																							15,900,000
PENNSYLVANIA | WP
Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																						115,500,000
PENNSYLVANIA | WP | Subsequent Event
Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																							96,800,000
WEST VIRGINIA | MP and PE
Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																									65,800,000	104,000,000
Public Utilities, Requested Rate Increase (Decrease), Percentage																									5.70%	9.90%
Public Utilities, Requested Surcharge, Amount																										48,000,000
Utilities Operating Expense, Under-recovered Balance	51,600,000	14,200,000							14,200,000
Public Utilities, Approved Rate Increase, Deferred Amount																								16,800,000
WEST VIRGINIA | MP and PE | WVPSC | Rate Case
Regulatory Matters [Line Items]
Recovery Period																											5 years
Public Utilities, Requested Rate Increase (Decrease), Amount																											15,000,000
Deferred Storm and Property Reserve Deficiency, Noncurrent																											46,000,000
WEST VIRGINIA | MP and PE | WVPSC | ENEC
Regulatory Matters [Line Items]
Number of issues not settled																								2
Public Utilities, Approved Rate Increase, Deferred Period																								1 year
Public Utilities, Approved Rate Increase, Deferred Amount, Carrying Costs																								4.00%
Review Period																								2 years
California Claims Matters | FERC
Regulatory Matters [Line Items]
Settlement proposal claims		$ 190,000,000
Court proceedings from filed claims																												1