Commitments and Contingencies (Details) (USD $)	6 Months Ended				0 Months Ended													1 Months Ended		6 Months Ended	12 Months Ended													6 Months Ended		6 Months Ended		6 Months Ended						0 Months Ended					0 Months Ended	6 Months Ended					6 Months Ended																												6 Months Ended								6 Months Ended							6 Months Ended
	Jun. 30, 2014 T	May 15, 2014	Dec. 31, 2013	Jun. 30, 2014 Other Purchase Obligations [Member]	Apr. 12, 2012 Cotter Corporation [Member] Defendants	Feb. 28, 2012 Cotter Corporation [Member] Defendants	Jun. 30, 2014 Total Accrual For Environmental Loss Contingencies [Member]	Dec. 31, 2013 Total Accrual For Environmental Loss Contingencies [Member]	Jun. 30, 2014 Accrual For MGP Investigation And Remediation [Member]	Dec. 31, 2013 Accrual For MGP Investigation And Remediation [Member]	Jun. 30, 2014 Financial Standby Letter of Credit [Member]		Dec. 31, 2013 Sithe Guarantee [Member]	Jun. 30, 2014 Nuclear Insurance Premiums [Member]		Jun. 30, 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]	Jun. 30, 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]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Net Capacity Purchases [Member]		Jun. 30, 2014 Exelon Generation Co L L C [Member] Power Purchases [Member]		Jun. 30, 2014 Exelon Generation Co L L C [Member] Transmission Rights Purchases [Member]		Jun. 30, 2014 Exelon Generation Co L L C [Member] Public Utilities, Inventory, Fuel [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Other Purchase Obligations [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Perryman Construction [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Beebe Construction [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] FourmileConstructionMember [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Maximum [Member] MW	Jun. 30, 2013 Exelon Generation Co L L C [Member] Maximum [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Minimum [Member] MW	Jun. 30, 2013 Exelon Generation Co L L C [Member] Minimum [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Cotter Corporation [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Rossville ash site [Member]	Jun. 30, 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]	Jun. 30, 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]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Nuclear Insurance Premiums [Member]		Jun. 30, 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	Jun. 30, 2014 Commonwealth Edison Co [Member] Customers Claiments MGPSites	Dec. 31, 2013 Commonwealth Edison Co [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Renewable Energy Including Renewable Energy Credits [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Other Purchase Obligations [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Energy Supply Procurement [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Maximum [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Minimum [Member]	Jun. 30, 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]	Jun. 30, 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]	Jun. 30, 2014 Commonwealth Edison Co [Member] Financial Standby Letter of Credit [Member]		Jun. 30, 2014 Commonwealth Edison Co [Member] Trust Preferred Securities [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]		Jun. 30, 2014 PECO Energy Co [Member] MGPSites	Dec. 31, 2013 PECO Energy Co [Member]	Jun. 30, 2014 PECO Energy Co [Member] DSP Program Electric Procurement Contracts [Member]		Jun. 30, 2014 PECO Energy Co [Member] Alternative Energy Credits [Member]		Jun. 30, 2014 PECO Energy Co [Member] Public Utilities, Inventory, Fuel [Member]	Jun. 30, 2014 PECO Energy Co [Member] Other Purchase Obligations [Member]	Jun. 30, 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]	Jun. 30, 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]	Jun. 30, 2014 PECO Energy Co [Member] Financial Standby Letter of Credit [Member]		Jun. 30, 2014 PECO Energy Co [Member] Trust Preferred Securities [Member]	Jun. 30, 2014 PECO Energy Co [Member] Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]		Jun. 30, 2014 Baltimore Gas and Electric Company [Member] MGPSites Claiments	Jun. 30, 2012 Baltimore Gas and Electric Company [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] Curtailment Services [Member]		Jun. 30, 2014 Baltimore Gas and Electric Company [Member] Public Utilities, Inventory, Fuel [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] Other Purchase Obligations [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] Energy Supply Procurement [Member]		Jun. 30, 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]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] Financial Standby Letter of Credit [Member]		Jun. 30, 2014 Baltimore Gas and Electric Company [Member] Trust Preferred Securities [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]		Jun. 30, 2014 Midwest Generation, LLC [Member]
Commercial Commitments [Abstract]
Guarantee Obligations Maximum Exposure	$ 9,839,000,000										$ 1,514,000,000	[1]	$ 200,000,000	$ 3,559,000,000	[2]	$ 4,706,000,000	[3]			$ 6,375,000,000																						$ 1,470,000,000	[1]		$ 3,559,000,000	[2]	$ 1,346,000,000	[4]		$ 225,000,000											$ 19,000,000	[1]	$ 200,000,000	$ 206,000,000	[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]
Estimated net exposure for commercial transaction obligations																600,000,000																															300,000,000
UnderwritingDiscount	60,000,000
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																						3,600,000,000																							2,700,000,000
Spent Nuclear Fuel Obligation [Abstract]
Cost of spent nuclear fuel disposal per kWh of net nuclear generation																				0.001
NetNuclearFuelDisposalFees																				49,000,000	136,000,000
LossContingencySettlementAbstract
Receivable from affiliate																																																		2,606,000,000	2,469,000,000															490,000,000	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							323,000,000	338,000,000	258,000,000	273,000,000																														56,000,000	56,000,000																222,000,000	234,000,000	217,000,000	229,000,000														44,000,000	47,000,000	41,000,000	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																				15,000,000	14,000,000																																																																													9,000,000
Environmental Issues - Air [Abstract]
States subject to the Cross State Air Pollution Rule																				28
Emissions allowance balance																				64,000,000
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Net investment in long-term direct financing leases	353,000,000		698,000,000
Coal Rail Car Lease Proof of Claims																																																		21,000,000
Probable contingency (liability)																				21,000,000
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																				104,000,000	90,000,000
Asbestos liability reserve related to open claims																				21,000,000
Open asbestos liability claims																				247
Asbestos liability reserve related to anticipated claims																				83,000,000
Increase (decrease) in the value of the asbestos liability reserve																				15,000,000	25,000,000																																																																													6,000,000
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				140,000,000																264,000,000			208,000,000	[8]	43,000,000	[9]	13,000,000	[10]	694,000,000	110,000,000		53,000,000	38,000,000																			32,000,000	16,000,000	217,000,000														381,000,000	[11]	1,000,000	[12]	90,000,000	12,000,000												21,000,000	[13]	64,000,000	1,000,000	448,000,000	[14]
Purchase Obligations, Due within Two Years				171,000,000																529,000,000			353,000,000	[8]	163,000,000	[9]	13,000,000	[10]	1,526,000,000	155,000,000	84,000,000																					73,000,000	8,000,000	232,000,000														169,000,000	[11]	2,000,000	[12]	112,000,000	4,000,000												40,000,000	[13]	83,000,000	4,000,000	632,000,000	[14]
Purchase Obligations, Due within Three Years				65,000,000																393,000,000			269,000,000	[8]	122,000,000	[9]	2,000,000	[10]	1,230,000,000	52,000,000																						76,000,000	5,000,000	151,000,000																2,000,000	[12]	93,000,000	3,000,000												34,000,000	[13]	82,000,000	5,000,000	240,000,000	[14]
Purchase Obligations, Due within Four Years				55,000,000																269,000,000			208,000,000	[8]	59,000,000	[9]	2,000,000	[10]	1,276,000,000	47,000,000																						77,000,000	5,000,000	140,000,000																2,000,000	[12]	35,000,000	1,000,000										2,000,000		29,000,000	[13]	65,000,000
Purchase Obligations, Due within Five Years				37,000,000																113,000,000			98,000,000	[8]	13,000,000	[9]	2,000,000	[10]	929,000,000	31,000,000																						78,000,000	5,000,000																	2,000,000	[12]	15,000,000	1,000,000												12,000,000	[13]	53,000,000
Purchase Obligations, Due after Five Years				100,000,000																424,000,000			388,000,000	[8]	4,000,000	[9]	32,000,000	[10]	4,318,000,000	79,000,000																						1,212,000,000	14,000,000																	4,000,000	[12]	66,000,000	7,000,000														271,000,000
Purchase Obligations, Total				568,000,000																1,992,000,000			1,524,000,000	[8]	404,000,000	[9]	64,000,000	[10]	9,973,000,000	474,000,000																						1,548,000,000	53,000,000	740,000,000														550,000,000	[11]	13,000,000	[12]	411,000,000	28,000,000												136,000,000	[13]	618,000,000	12,000,000	1,320,000,000	[14]
Unrecorded Unconditional Purchase Obligation, Additional Information [Abstract]
Percentage of ownership interest in CENG (as a percent)		67.00%																		50.01%
Operating Leases Future Minimum Payments Due Table [Abstract]
Minimum future operating lease payments due in three years																				9,000,000
Minimum future operating lease payments due in four years																				12,000,000
Minimum future operating lease payments due in five years																				12,000,000
Minimum future operating lease payments due beyond five years																				$ 270,000,000

[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, including CENG sites, 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 miscellaneous guarantees. The estimated net exposure for obligations under commercial transactions covered by these guarantees was $0.6 billion at June 30, 2014, which represents the total amount Exelon could be required to fund based on June 30, 2014 market prices.

[4] Primarily reflects guarantees issued to ensure performance under energy marketing and other specific contracts. The estimated net exposure for obligations under commercial transactions covered by these guarantees was $0.3 billion at June 30, 2014, which represents the total amount Generation could be required to fund based on June 30, 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 June 30, 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] 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 5 - Regulatory Matters for additional information.

[12] PECO is subject to requirements related to the use of alternative energy resources established by the AEPS Act. See Note 5 - Regulatory Matters for additional information.

[13] BGE has entered into various contracts with curtailment services providers related to transactions in PJM's capacity market. See Note 5 - Regulatory Matters for additional information

[14] BGE has entered into various contracts with curtailment services providers related to transactions in PJM's capacity market. See Note 5 - Regulatory Matters for additional information.