Merger and Acquisitions (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	0 Months Ended	1 Months Ended	3 Months Ended			6 Months Ended							3 Months Ended		6 Months Ended				6 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			0 Months Ended	3 Months Ended			6 Months Ended
	May 15, 2014	Jun. 30, 2014	Jun. 30, 2014	Sep. 30, 2013	Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013		Apr. 02, 2014	Jun. 30, 2014 Severance [Member]	Dec. 31, 2013 Severance [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Severance [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member] Severance [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] Maximum [Member] MW	Jun. 30, 2013 Exelon Generation Co L L C [Member] Maximum [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member]	Jun. 30, 2014 PECO Energy Co [Member]	Jun. 30, 2013 PECO Energy Co [Member]	Jun. 30, 2014 PECO Energy Co [Member]	Jun. 30, 2013 PECO Energy Co [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member]	Jun. 30, 2012 Baltimore Gas and Electric Company [Member]	May 15, 2014 Pepco Holdings [Member]	Jun. 30, 2014 Pepco Holdings [Member]	Jun. 11, 2014 Pepco Holdings [Member]	Jun. 11, 2014 Pepco Holdings [Member] Convertible	Jun. 30, 2014 Pepco Holdings [Member] Minimum [Member]	Jun. 30, 2014 Pepco Holdings [Member] Maximum [Member]	Jun. 30, 2014 Customer Relationships [Member] Constellation Energy Group Acquisition [Member]	Jun. 30, 2014 Trade Names [Member] Constellation Energy Group Acquisition [Member]	Jun. 30, 2014 Power Supply Contracts [Member] Constellation Energy Group Acquisition [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite Lived Intangible Asset Weighted Average Useful Life																																										12 years 4 months 26 days	10 years	1 year 6 months 3 days
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition Cost Of Acquired Entity Transaction Costs																																					$ 25,000,000
Payments To Acquire Businesses Net Of Cash Acquired [Abstract]
Payments To Acquire Businesses Gross						66,000,000		3,000,000							(66,000,000)
BusinessAcquisitionPreexistingRelationshipGainLossRecognized		125,000,000	125,000,000			125,000,000
Business Combination Proposed Customer Benefits Package																																					100,000,000
BusinessExitCosts																																								259,000,000	293,000,000
CashFundingFromNonCoreAssetSale																																					1,000,000
Units of shares offered		57.5
SubordinatedLongTermDebt																																							1,200,000,000
BridgeLoan		4,200,000,000	4,200,000,000			4,200,000,000				7,200,000,000
Equity Method Investment Ownership Percentage	67.00%												50.01%		50.01%
GainOnSaleOfInvestmentsNet																																				332,000,000
EquityMethodInvestmentNetSalesProceeds																																				613,000,000
AfterTaxNetCashProceeds	37,000,000
Cash offered in exchange for each share of PHI common stock																																					$ 27.25	$ 35
PHI Preferred Securities Acquired																																					90,000,000
OtherLongTermInvestmentsMaximum																																					180,000,000
Long Term Debt		131,000,000	131,000,000			131,000,000							1,000,000		1,000,000
Business Acquisition, Impact Of Merger [Abstract]
Revenues			6,024,000,000	6,141,000,000	6,141,000,000	13,261,000,000	[1]	12,223,000,000	[1]				3,789,000,000	4,070,000,000	8,179,000,000	7,603,000,000							1,128,000,000	1,080,000,000	2,262,000,000	2,239,000,000	656,000,000	672,000,000	1,649,000,000	1,567,000,000	653,000,000	653,000,000	1,707,000,000	1,533,000,000
Net income			557,000,000		497,000,000			498,000,000					372,000,000	328,000,000	188,000,000	310,000,000							111,000,000	96,000,000	209,000,000	14,000,000	84,000,000	78,000,000	173,000,000	200,000,000	19,000,000	25,000,000	106,000,000	106,000,000
Regulatory Assets Transfer Changes																																	8,000,000
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																				95,000,000		120,000,000
Business Acquisition, Development Of New Generation Cost																			600,000,000		650,000,000
Business Acquisition, Expected New Generation Mwh																			285		300
Business Acquisition Potential Cash Payment		40,000,000	40,000,000			40,000,000
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Start											20,000,000	2,000,000					20,000,000	2,000,000
Severance Charges						2,000,000									2,000,000
Payments						3,000,000									3,000,000
Restructuring Reserve, Period End											20,000,000	2,000,000					20,000,000	2,000,000
Business Acquisition, Costs Recognized Post Merger [Abstract]
Length of years for charitable contributions at $7 million per year						10 years
Business Acquisition Charitable Contributions Per Year						$ 7,000,000

[1] For the six months ended June 30, 2014 and 2013, utility taxes of $45 million and $39 million, respectively, are included in revenues and expenses for Generation. For the six months ended June 30, 2014 and 2013, utility taxes of $119 million and $117 million, respectively, are included in revenues and expenses for ComEd. For the six months ended June 30, 2014 and 2013, utility taxes of $65 million and $64 million, respectively, are included in revenues and expenses for PECO. For the six months ended June 30, 2014 and 2013, utility taxes of $43 million and $41 million, respectively, are included in revenues and expenses for BGE.