Commitments and Contingencies (Details) (USD $)	3 Months Ended	12 Months Ended		0 Months Ended											3 Months Ended		1 Months Ended		3 Months Ended																3 Months Ended		3 Months Ended		3 Months Ended						0 Months Ended			3 Months Ended		0 Months Ended	3 Months Ended							3 Months Ended																												3 Months Ended								3 Months Ended
	Mar. 31, 2014 T	Dec. 31, 2013	Mar. 31, 2014 Other Purchase Obligations [Member]	Apr. 12, 2012 Cotter Corporation [Member] Defendants	Feb. 28, 2012 Cotter Corporation [Member] Defendants	Mar. 31, 2014 Total Accrual For Environmental Loss Contingencies [Member]	Dec. 31, 2013 Total Accrual For Environmental Loss Contingencies [Member]	Mar. 31, 2014 Accrual For MGP Investigation And Remediation [Member]	Dec. 31, 2013 Accrual For MGP Investigation And Remediation [Member]	Mar. 31, 2014 Financial Standby Letter of Credit [Member]		Dec. 31, 2013 Sithe Guarantee [Member]	Mar. 31, 2014 Nuclear Insurance Premiums [Member]		Mar. 31, 2014 Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]		Jan. 31, 2013 Exelon Generation Co L L C [Member]	Oct. 31, 2007 Exelon Generation Co L L C [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Reactors States OpenClaims	Dec. 31, 2013 Exelon Generation Co L L C [Member]	Jan. 31, 2005 Exelon Generation Co L L C [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Net Capacity Purchases [Member]		Mar. 31, 2014 Exelon Generation Co L L C [Member] Power Purchases [Member]		Mar. 31, 2014 Exelon Generation Co L L C [Member] Transmission Rights Purchases [Member]		Mar. 31, 2014 Exelon Generation Co L L C [Member] Purchased Energy from Equity Investment [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Public Utilities, Inventory, Fuel [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Solar Facility Construction [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Other Purchase Obligations [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Perryman Construction [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Beebe Construction [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] FourmileConstructionMember [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Maximum [Member] MW	Mar. 31, 2013 Exelon Generation Co L L C [Member] Maximum [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Minimum [Member] MW	Mar. 31, 2013 Exelon Generation Co L L C [Member] Minimum [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Cotter Corporation [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Rossville ash site [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Total Accrual For Environmental Loss Contingencies [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member] Total Accrual For Environmental Loss Contingencies [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Financial Standby Letter of Credit [Member]		Jan. 31, 2005 Exelon Generation Co L L C [Member] Sithe Guarantee [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Nuclear Insurance Premiums [Member]		Mar. 31, 2014 Exelon Generation Co L L C [Member] Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]		Jul. 11, 2011 Commonwealth Edison Co [Member] Customers	Mar. 31, 2014 Commonwealth Edison Co [Member] ElectricGenerationStation Claiments Customers MGPSites	Dec. 31, 2013 Commonwealth Edison Co [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Renewable Energy Including Renewable Energy Credits [Member]		Mar. 31, 2014 Commonwealth Edison Co [Member] Other Purchase Obligations [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Energy Supply Procurement [Member]		Mar. 31, 2014 Commonwealth Edison Co [Member] Maximum [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Minimum [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Total Accrual For Environmental Loss Contingencies [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Total Accrual For Environmental Loss Contingencies [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Accrual For MGP Investigation And Remediation [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Accrual For MGP Investigation And Remediation [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Financial Standby Letter of Credit [Member]		Mar. 31, 2014 Commonwealth Edison Co [Member] Trust Preferred Securities [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]		Mar. 31, 2014 PECO Energy Co [Member] MGPSites	Dec. 31, 2013 PECO Energy Co [Member]	Mar. 31, 2014 PECO Energy Co [Member] DSP Program Electric Procurement Contracts [Member]		Mar. 31, 2014 PECO Energy Co [Member] Alternative Energy Credits [Member]		Mar. 31, 2014 PECO Energy Co [Member] Public Utilities, Inventory, Fuel [Member]	Mar. 31, 2014 PECO Energy Co [Member] Other Purchase Obligations [Member]	Mar. 31, 2014 PECO Energy Co [Member] Total Accrual For Environmental Loss Contingencies [Member]	Dec. 31, 2013 PECO Energy Co [Member] Total Accrual For Environmental Loss Contingencies [Member]	Mar. 31, 2014 PECO Energy Co [Member] Accrual For MGP Investigation And Remediation [Member]	Dec. 31, 2013 PECO Energy Co [Member] Accrual For MGP Investigation And Remediation [Member]	Mar. 31, 2014 PECO Energy Co [Member] Financial Standby Letter of Credit [Member]		Mar. 31, 2014 PECO Energy Co [Member] Trust Preferred Securities [Member]	Mar. 31, 2014 PECO Energy Co [Member] Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]		Mar. 31, 2014 Baltimore Gas and Electric Company [Member] MGPSites Claiments	Mar. 31, 2012 Baltimore Gas and Electric Company [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Curtailment Services [Member]		Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Public Utilities, Inventory, Fuel [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Other Purchase Obligations [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Energy Supply Procurement [Member]		Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Sixty-Eighth Street Dump [Member] PrincipleResponsibleParties	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Total Accrual For Environmental Loss Contingencies [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Financial Standby Letter of Credit [Member]		Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Trust Preferred Securities [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]		Mar. 31, 2014 Midwest Generation, LLC [Member]
Commercial Commitments [Abstract]
Guarantee Obligations Maximum Exposure	$ 9,890,000,000									$ 1,717,000,000	[1]	$ 200,000,000	$ 3,529,000,000	[2]	$ 4,644,000,000	[3]			$ 6,491,000,000																								$ 1,675,000,000	[1]		$ 3,529,000,000	[2]	$ 1,287,000,000	[4]		$ 222,000,000													$ 17,000,000	[1]	$ 200,000,000	$ 205,000,000	[5]	$ 203,000,000												$ 22,000,000	[1]	$ 178,000,000	$ 181,000,000	[6]	$ 260,000,000										$ 1,000,000	[1]	$ 250,000,000	$ 259,000,000	[7]
Commercial Commitments Footnote [Abstract]
Guarantees in support of equity investment															211,000,000																																	211,000,000
Estimated net exposure for commercial transaction obligations															500,000,000																																	300,000,000
Nuclear Insurance [Abstract]
Nuclear insurance liability limit per incident																																														13,600,000,000
Required nuclear liability insurance per site																			375,000,000
Total of U.S. licensed nuclear reactors																			104
Nuclear financial protection pool value																			13,200,000,000
Maximum assessment mandated by Price-Anderson Act per nuclear reactor for a nuclear incident																																														127,300,000,000
Maximum annual assessment payment mandated by Price-Anderson Act for a nuclear incident																																														19,000,000
Maximum liability per nuclear incident																					3,500,000,000																									2,400,000,000
Spent Nuclear Fuel Obligation [Abstract]
Cost of spent nuclear fuel disposal per kWh of net nuclear generation																			0.001
NetNuclearFuelDisposalFees																			136,000,000
LossContingencySettlementAbstract
Receivable from affiliate																																																			2,497,000,000	2,469,000,000																	455,000,000	447,000,000
Guarantees Related To Indemnifications [Abstract]
Acquisition of interest in subsidiary																																													50.00%
Sale of interest in subsidiary																																													100.00%
Business Acquisition, Regulatory Matters [Abstract]
Business Acquisition, Direct Investment With State And Local Governments Due To Settlement																																																																																							1,000,000,000
Business Acquisition, Construction Cost																																				120,000,000		95,000,000
Business Acquisition, Development Of New Generation Cost																																			650,000,000		600,000,000
Business Acquisition, Expected New Generation Mwh																																			300		285
Business Acquisition Potential Cash Payment	40,000,000
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities						332,000,000	338,000,000	267,000,000	273,000,000																																56,000,000	56,000,000																		230,000,000	234,000,000	225,000,000	229,000,000														45,000,000	47,000,000	42,000,000	44,000,000						1,000,000									1,000,000
Environmental Issues - MGP Site Contingency [Abstract]
Total number of MGP sites																																																			42																		26																	13
Approved clean-up																																																			16																		16
Sites under study/remediation																																																			26																		10																	2
Environmental Issues - Water [Abstract]
Low end of range of cooling tower cost	430,000,000																		430,000,000
Consent decree penalty																		1,000,000
Environmental loss contingencies																		30,000,000	15,000,000																																																																																		8,000,000
Increase in accrual due to purchase accounting																			3,000,000
Increase in accrual due to an update of costs																			2,000,000
Environmental Issues - Air [Abstract]
States subject to the Cross State Air Pollution Rule																			28
Emissions allowance balance																			51,000,000
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Net investment in long-term direct financing leases	368,000,000	698,000,000
Number Of Stations Violating Clean Air Act																																																			6
Coal Rail Car Lease Proof of Claims																																																			21,000,000
Probable contingency (liability)																			20,000,000
Midwest Generation's estimated environmental investigation and remediation costs																																																																																																					53,000,000
Payments for operating leases																	10,000,000
Environmental Issues - Solid and Hazardous Waste [Abstract]
DOJ potential settlement																																							90,000,000
Total cost of remediation to be shared by PRPs																																							42,000,000																																															1,700,000
Loss Contingency Number Of Defendants				14	15
Loss Contingency Number Of Parties Jointly And Severally Liable In Environmental Protection Agency Action																																																																																														19
Loss Contingency Esitmate to close site																																								6,000,000
68th Street and Sauer Dumps [Abstract]
Number of defendants in addition to BGE and Constellation Energy																																																																																														19
Minimum estimated clean-up costs for all potentially responsible parties																																																																																														50,000,000
Maximum estimated clean-up costs for all potentially responsible parties																																																																																						1,700,000								64,000,000
Climate Change Regulation [Abstract]
Minimum GHG emissions by stationary sources to qualify for regulation	100,000
Minimum additional GHG emissions by stationary sources after a modification	75,000
Effective Number Of Years For Tailoring Rule	6 years
Asbestos Loss Contingency [Abstract]
Asbestos liability reserve																			89,000,000	90,000,000
Asbestos liability reserve related to open claims																			20,000,000
Open asbestos liability claims																			238
Asbestos liability reserve related to anticipated claims																			69,000,000
Increase (decrease) in the value of the asbestos liability reserve		25,000,000
Asbestos reserve adjustment
Number of claimants																																																																																						486
Continuous Power Interruption [Abstract]
Minimum number of customers ComEd can be held liable to for power interruption																																																			30,000
Number of customers affected by a major storm																																																		900,000
Number of customers proposed by the ICC that ComEd should not be granted a waiver under Continuous Power Interruption																																																		34,559
Telephone Consumer Protection Act Lawsuit [Abstract]
PossibleDefendantsNumber																																																			1,200,000
LossContingencyDamagesSought																																																										1,500	500
Business Acquisition, Regulatory Matters [Abstract]
Business Acquisition, Direct Investment With State And Local Governments Due To Settlement																																																																																							1,000,000,000
Business Acquisition, Construction Cost																																				120,000,000		95,000,000
Business Acquisition, Development Of New Generation Cost																																			650,000,000		600,000,000
Business Acquisition, Expected New Generation Mwh																																			300		285
Business Acquisition Potential Cash Payment	40,000,000
Unrecorded Unconditional Purchase Obligation [Abstract]
Purchase Obligations, Due within One Year			150,000,000																1,073,000,000			314,000,000	[8]	100,000,000	[9]	19,000,000	[10]	640,000,000	1,036,000,000	90,000,000	120,000,000		47,000,000	27,000,000																			50,000,000	[11]	11,000,000	178,000,000	[12]														546,000,000	[13]	2,000,000	[14]	146,000,000	16,000,000												33,000,000	[15]	105,000,000	1,000,000	541,000,000	[16]
Purchase Obligations, Due within Two Years			146,000,000																521,000,000			367,000,000	[8]	141,000,000	[9]	13,000,000	[10]	0	1,285,000,000		138,000,000	80,000,000																					72,000,000	[11]	5,000,000	136,000,000	[12]														167,000,000	[13]	2,000,000	[14]	117,000,000	1,000,000												40,000,000	[15]	82,000,000	2,000,000	409,000,000	[16]
Purchase Obligations, Due within Three Years			58,000,000																382,000,000			284,000,000	[8]	96,000,000	[9]	2,000,000	[10]	0	1,039,000,000		45,000,000																						76,000,000	[11]	5,000,000	137,000,000	[12]																2,000,000	[14]	98,000,000	3,000,000												34,000,000	[15]	80,000,000	5,000,000	76,000,000	[16]
Purchase Obligations, Due within Four Years			49,000,000																267,000,000			223,000,000	[8]	42,000,000	[9]	2,000,000	[10]		1,041,000,000		41,000,000																						77,000,000	[11]	5,000,000	140,000,000	[12]																2,000,000	[14]	37,000,000	1,000,000										2,000,000		13,000,000	[15]	63,000,000
Purchase Obligations, Due within Five Years			36,000,000																122,000,000			112,000,000	[8]	8,000,000	[9]	2,000,000	[10]		780,000,000		30,000,000																						83,000,000	[11]	5,000,000																		2,000,000	[14]	15,000,000	1,000,000												0		52,000,000
Purchase Obligations, Due after Five Years			108,000,000																450,000,000			414,000,000	[8]	4,000,000	[9]	32,000,000	[10]		3,221,000,000		88,000,000																						1,207,000,000	[11]	14,000,000																		4,000,000	[14]	66,000,000	6,000,000														258,000,000
Purchase Obligations, Total			$ 547,000,000																$ 2,815,000,000			$ 1,714,000,000	[8]	$ 391,000,000	[9]	$ 70,000,000	[10]	$ 640,000,000	$ 8,402,000,000		$ 462,000,000																						$ 1,565,000,000	[11]	$ 45,000,000	$ 591,000,000	[12]														$ 713,000,000	[13]	$ 14,000,000	[14]	$ 479,000,000	$ 28,000,000												$ 120,000,000	[15]	$ 640,000,000	$ 10,000,000	$ 1,026,000,000	[16]
Unrecorded Unconditional Purchase Obligation, Additional Information [Abstract]
Percentage of ownership interest in CENG (as a percent)																			50.01%

[1] Non-debt letters of credit maintained to provide credit support for certain transactions as requested by third parties.

[2] Represents the maximum amount that Generation would be required to pay for retrospective premiums in the event of nuclear disaster at any domestic site under the Secondary Financial Protection pool as required under the Price-Anderson Act as well as the current aggregate annual retrospective premium obligation that could be imposed by NEIL. See the Nuclear Insurance section within this note for additional details on Generation’s nuclear insurance premiums.

[3] Primarily reflects parental guarantees issued on behalf of Generation to allow the flexibility needed to conduct business with counterparties without having to post other forms of collateral. Also reflects guarantees issued to ensure performance under specific contracts, preferred securities of financing trusts, property leases, indemnifications, NRC minimum funding assurance requirements and $211 million on behalf of CENG nuclear generating facilities for credit support and miscellaneous guarantees. The estimated net exposure for obligations under commercial transactions covered by these guarantees was $0.5 billion at March 31, 2014, which represents the total amount Exelon could be required to fund based on March 31, 2014 market prices.

[4] Primarily reflects guarantees issued to ensure performance under energy marketing and other specific contracts and $211 million on behalf of CENG nuclear generating facilities for credit support. The estimated net exposure for obligations under commercial transactions covered by these guarantees was $0.3 billion at March 31, 2014, which represents the total amount Generation could be required to fund based on March 31, 2014 market prices.

[5] Primarily reflects full and unconditional guarantees of $200 million Trust Preferred Securities of ComEd Financing III, which is a 100% owned finance subsidiary of ComEd.

[6] Primarily reflects full and unconditional guarantees of $178 million Trust Preferred Securities of PECO Trust III and IV, which are 100% owned finance subsidiaries of PECO.

[7] Primarily reflects full and unconditional guarantees of $250 million Trust Preferred Securities of BGE Capital Trust II, which is a 100% owned finance subsidiary of BGE.

[8] Net capacity purchases include PPAs and other capacity contracts including those that are accounted for as operating leases. Amounts presented in the commitments represent Generation's expected payments under these arrangements at March 31, 2014, net of fixed capacity payments expected to be received by Generation under contracts to resell such acquired capacity to third parties under long-term capacity sale contracts.

[9] The table excludes renewable energy purchases that are contingent in nature.

[10] Transmission rights purchases include estimated commitments for additional transmission rights that will be required to fulfill firm sales contracts.

[11] (b)        ComEd entered into 20-year contracts for renewable energy and RECs beginning in June 2012. ComEd is permitted to recover its renewable energy and REC costs from retail customers with no mark-up. The commitments represent the maximum settlements with suppliers for renewable energy and RECs under the existing contract terms. Pursuant to the ICC’s Order on December 19, 2012, ComEd’s commitments under the existing long-term contracts were reduced for the June 2013 through May 2014 procurement period. In addition, the ICC’s December 18, 2013 order approved the reduction of ComEd’s commitments under those contracts for the June 2014 through May 2015 procurement period, and the amount of the reduction was approved by the ICC in March 2014.

[12] (a)        ComEd entered into various contracts for the procurement of electricity that started to expire in 2012, and will continue to expire through 2017. ComEd is permitted to recover its electric supply procurement costs from retail customers with no mark-up.

[13] PECO entered into various contracts for the procurement of electric supply to serve its default service customers that expire between 2014 and 2016. PECO is permitted to recover its electric supply procurement costs from default service customers with no mark-up in accordance with its PAPUC-approved DSP Programs. See Note 4 - Regulatory Matters for additional information.

[14] PECO is subject to requirements related to the use of alternative energy resources established by the AEPS Act. See Note 4 - Regulatory Matters for additional information.

[15] BGE has entered into various contracts with curtailment services providers related to transactions in PJM's capacity market. See Note 4 - Regulatory Matters for additional information

[16] BGE has entered into various contracts with curtailment services providers related to transactions in PJM's capacity market. See Note 4 - Regulatory Matters for additional information.