Regulatory Matters (Details) (USD $)	3 Months Ended	1 Months Ended	3 Months Ended					0 Months Ended	3 Months Ended	0 Months Ended			31 Months Ended	0 Months Ended	3 Months Ended					1 Months Ended	3 Months Ended		12 Months Ended	3 Months Ended						12 Months Ended							1 Months Ended	3 Months Ended			1 Months Ended			3 Months Ended
	Mar. 31, 2013 entities	Apr. 30, 2007 FERC kv	Mar. 31, 2013 FERC class	Jan. 21, 2010 FERC issues	Dec. 07, 2012 FERC MOPR Reform exemption	Dec. 20, 2012 FERC Synchronous Condensers	Mar. 31, 2013 FERC PJM	Aug. 24, 2012 FERC PATH	Mar. 31, 2013 FERC PATH kv	Aug. 24, 2012 FERC PATH-Allegheny	Aug. 24, 2012 FERC Path-WV	Jun. 30, 2011 FERC Path-WV challenge	Dec. 31, 2012 FERC FES and AE FTR Underfunding Complaint Minimum	Dec. 22, 2011 MARYLAND	Mar. 31, 2013 MARYLAND	Aug. 31, 2011 MARYLAND	Oct. 06, 2009 MARYLAND	Feb. 22, 2013 NEW JERSEY	Nov. 30, 2012 NEW JERSEY	Aug. 31, 2011 OHIO proposals	Mar. 31, 2013 OHIO plan	Oct. 31, 2009 OHIO proposals	Dec. 31, 2009 OHIO	Mar. 31, 2013 OHIO Year 2012 MWh	Mar. 31, 2013 OHIO Year 2013 MWh	Mar. 31, 2013 OHIO Year 2014 MWh	Mar. 31, 2013 OHIO Annually Through 2025 MWh	Mar. 31, 2013 OHIO Annually Through 2018	Mar. 31, 2013 PENNSYLVANIA	Dec. 31, 2010 PENNSYLVANIA	Feb. 15, 2013 PENNSYLVANIA choice	Jan. 16, 2013 PENNSYLVANIA issues Party	May 31, 2011 PENNSYLVANIA	Apr. 29, 2011 PENNSYLVANIA questions	Mar. 31, 2013 PENNSYLVANIA Statutory Penalty	Mar. 31, 2013 PENNSYLVANIA Year 2013	Apr. 30, 2010 WEST VIRGINIA	Mar. 31, 2013 WEST VIRGINIA MW	Oct. 22, 2012 WEST VIRGINIA hearing	Feb. 28, 2011 WEST VIRGINIA Facilities	Feb. 28, 2011 WEST VIRGINIA City of New Martinsville entities	Feb. 28, 2011 WEST VIRGINIA Morgantown Energy entities	Oct. 31, 2006 California Claims Matters FERC Proceedings	Mar. 31, 2013 California Claims Matters FERC	Mar. 31, 2013 Yards Creek Pumped Storage Project FERC MW	Mar. 31, 2013 Yards Creek Pumped Storage Project FERC JCP&L	Mar. 31, 2013 The Seneca Pumped Storage Project FERC MW	Mar. 31, 2013 The Seneca Pumped Storage Project Relicensing
Regulatory Matters [Line Items]
Proposed electric consumption reduction percentage															10.00%
Proposed electric demand reduction percentage															15.00%
Expenditures for cost recovery program																$ 66,000,000	$ 101,000,000
Recovery period for expenditures for cost recovery program														5 years	3 years
Maximum penalty assessed, in dollars per day per violation															25,000
Expected increase in cost due to proposed plan															106,000,000
Requested increase in revenues																		603,000,000	31,500,000
Increase in revenue recovery request																		112,000,000
Number of cost recovery choices																															2
Load cap percentage minimum																					80.00%
Maximum trance award to a single supplier																					80.00%
Generation discount for low income customers																					6.00%
Costs avoided by customers																					360,000,000
Fund to assist low income customers																					12,000,000
ESP extension term																					2 years
Generation supply auction period, after approval																					3 years
Generation supply auction period, before approval																					1 year
Annual energy savings																								1,211,000	1,726,000	2,306,000	2,903,000
Increase (decrease) in annual energy savings																								416,000
Utilities required to reduce peak demand																							1.00%
Utilities required to additionally reduce peak demand																												0.75%
Period of the portfolio plans filed seeking approval for the program																							3 years
Number of plans																					3
Portfolio plan, estimated cost																					250,000,000
Request for proposals conducted																				2		3
Marginal transmission refund period																													29 months
Marginal transmission losses																														254,000,000
Minimum reduction in Utilities reduce energy consumption																																	1.00%			3.00%
Minimum reduction in Utilities peak demand																																				4.50%
Loss contingency, maximum																																			20,000,000
Directed questions for investigation																																		11
Number of parties not settled																																1
Number of issues not settled																																1
Percent of Meters to be Installed																													98.50%
Expected Cost of Meter Installations																													1,250,000,000
Annualized base rate increase																																					40,000,000
Storm restoration deferral period																																					5 years
Number of public hearings held																																							2
Period of time to implement plan																																						6 months
Period of time to file case																																						6 months
Additional base rate increase																																					20,000,000
Decrease in ENEC rates																																					20,000,000
Number of electric generation facilities																																								3
Number of electric generation facilities, owned by third party																																									1	1
Resource plan, proposed transfer																																						1,476
Annual load growth rate																																						1.40%
Regional enforcement entities	8
Power threshold for cost methodology		500
Denied Recovery Charges of Exit Fees			78,800,000
Identified issues for written comments				9
Hybrid methodology, beneficiary pays cost allocation							50.00%
Hybrid methodology, postage stamp cost allocation							50.00%
Annual Revenue requirements in Zone			16,000,000
Number of classes of regulatory proceedings			2
Settlement proposal claims																																												190,000,000
Court proceedings from filed claims																																											1
New Voltage transmission facilities across PJM and a zonal transmission rate (In KV)									765
Cost recovery, PP&E reclassified to Regulatory Assets										62,000,000	59,000,000
Return on equity for cost recovery								10.90%
Base return on equity for cost recovery								10.40%
Return on equity for cost recovery from RTO membership								0.50%
Remaining Recovery Period of Regulatory Assets								5 years
Number of Formal Challenges												2
Hydroelectric project																																													400		451
Asset Transfer, Price						21,500,000
Ownership interest																																														50.00%
Renewal length of operating license																																														40 years
ILP licensure period																																														5 years
Period of cycle																																																5 years
Number of Exemptions Added					2
Estimated Conversion Costs						60,000,000
Revenues Lost of Which the Entity is Entitled													$ 57,000,000