Merger and Acquisitions (Details) (USD $)	3 Months Ended									12 Months Ended												3 Months Ended									12 Months Ended												3 Months Ended									12 Months Ended							3 Months Ended									12 Months Ended					3 Months Ended									12 Months Ended												0 Months Ended	12 Months Ended															12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2013 Severance [Member]	Dec. 31, 2012 Severance [Member]	Dec. 31, 2013 One-time Termination Benefits [Member]	Dec. 31, 2013 Other Severance Charges [Member]	Dec. 31, 2012 Other Severance Charges [Member]	Dec. 31, 2011 Other Severance Charges [Member]	Dec. 31, 2013 Minimum [Member] MW	Dec. 31, 2013 Maximum [Member] MW	Dec. 31, 2013 Exelon Generation Co L L C [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member]	Mar. 31, 2013 Exelon Generation Co L L C [Member]	Dec. 31, 2012 Exelon Generation Co L L C [Member]		Sep. 30, 2012 Exelon Generation Co L L C [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member]	Mar. 31, 2012 Exelon Generation Co L L C [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member]		Dec. 31, 2012 Exelon Generation Co L L C [Member]		Dec. 31, 2011 Exelon Generation Co L L C [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member] Severance [Member]	Dec. 31, 2012 Exelon Generation Co L L C [Member] Severance [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member] One-time Termination Benefits [Member]	Dec. 31, 2012 Exelon Generation Co L L C [Member] Stock Compensation Plan [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member] Other Severance Charges [Member]	Dec. 31, 2012 Exelon Generation Co L L C [Member] Other Severance Charges [Member]	Dec. 31, 2011 Exelon Generation Co L L C [Member] Other Severance Charges [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member]	Sep. 30, 2013 Commonwealth Edison Co [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member]	Mar. 31, 2013 Commonwealth Edison Co [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member]		Sep. 30, 2012 Commonwealth Edison Co [Member]	Jun. 30, 2012 Commonwealth Edison Co [Member]	Mar. 31, 2012 Commonwealth Edison Co [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member]		Dec. 31, 2011 Commonwealth Edison Co [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Severance [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Other Severance Charges [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Other Severance Charges [Member]	Dec. 31, 2013 PECO Energy Co [Member]	Sep. 30, 2013 PECO Energy Co [Member]	Jun. 30, 2013 PECO Energy Co [Member]	Mar. 31, 2013 PECO Energy Co [Member]	Dec. 31, 2012 PECO Energy Co [Member]		Sep. 30, 2012 PECO Energy Co [Member]	Jun. 30, 2012 PECO Energy Co [Member]	Mar. 31, 2012 PECO Energy Co [Member]	Dec. 31, 2013 PECO Energy Co [Member]	Dec. 31, 2012 PECO Energy Co [Member]		Dec. 31, 2011 PECO Energy Co [Member]	Dec. 31, 2012 PECO Energy Co [Member] Other Severance Charges [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member]	Sep. 30, 2013 Baltimore Gas and Electric Company [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member]	Mar. 31, 2013 Baltimore Gas and Electric Company [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member]		Sep. 30, 2012 Baltimore Gas and Electric Company [Member]	Jun. 30, 2012 Baltimore Gas and Electric Company [Member]	Mar. 31, 2012 Baltimore Gas and Electric Company [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member]		Dec. 31, 2011 Baltimore Gas and Electric Company [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Severance [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Severance [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Other Severance Charges [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Other Severance Charges [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Operating Revenues [Member]	Dec. 31, 2013 Constellation Energy Group Acquisition [Member] MW	Dec. 31, 2012 Constellation Energy Group Acquisition [Member]	Nov. 30, 2012 Constellation Energy Group Acquisition [Member]	Nov. 30, 2012 Constellation Energy Group Acquisition [Member] Common Stock [Member]	Dec. 31, 2013 Constellation Energy Group Acquisition [Member] Exelon Generation Co L L C [Member]	Dec. 31, 2012 Constellation Energy Group Acquisition [Member] Exelon Generation Co L L C [Member]	Dec. 31, 2013 Constellation Energy Group Acquisition [Member] Commonwealth Edison Co [Member]	Dec. 31, 2012 Constellation Energy Group Acquisition [Member] Commonwealth Edison Co [Member]	Dec. 31, 2013 Constellation Energy Group Acquisition [Member] PECO Energy Co [Member]	Dec. 31, 2012 Constellation Energy Group Acquisition [Member] PECO Energy Co [Member]	Dec. 31, 2013 Constellation Energy Group Acquisition [Member] Baltimore Gas and Electric Company [Member]	Dec. 31, 2012 Constellation Energy Group Acquisition [Member] Baltimore Gas and Electric Company [Member]	Dec. 31, 2011 Wolf Hollow Acquisition [Member]	Dec. 31, 2011 Wolf Hollow Acquisition [Member] Exelon Generation Co L L C [Member] MW	Dec. 31, 2011 Antelope Valley Solar Ranch One Acquisition [Member]		Dec. 31, 2013 Antelope Valley Solar Ranch One Acquisition [Member] Exelon Generation Co L L C [Member] NumberOfHomes SolarPanels	Dec. 31, 2011 Antelope Valley Solar Ranch One Acquisition [Member] Exelon Generation Co L L C [Member] MW	Dec. 31, 2012 Antelope Valley Solar Ranch One Acquisition [Member] Exelon Generation Co L L C [Member]	Dec. 31, 2013 Customer Relationships [Member] Constellation Energy Group Acquisition [Member]	Dec. 31, 2013 Trade Names [Member] Constellation Energy Group Acquisition [Member]	Dec. 31, 2012 Trade Names [Member] Constellation Energy Group Acquisition [Member]	Dec. 31, 2012 Power Supply Contracts [Member]	Dec. 31, 2013 Power Supply Contracts [Member] Constellation Energy Group Acquisition [Member]		Dec. 31, 2012 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	[1]
Finite Lived Intangible Assets Net [Abstract]
Finite lived intangible assets gross	$ 576,000,000									$ 576,000,000																																																																																	$ 1,956,000,000																			$ 214,000,000	$ 243,000,000			$ 1,499,000,000	[1]
Finite lived intangible assets accumulated amortization	(159,000,000)									(159,000,000)																																																																																	(1,460,000,000)																			(36,000,000)	(46,000,000)			(1,378,000,000)	[1]
Finite lived intangible assets net	417,000,000									417,000,000																																																																																	496,000,000																			178,000,000	197,000,000			121,000,000	[1]
Amortization Of Contracts																																																																																											470,000,000	1,101,000,000																			26,000,000	20,000,000		21,000,000		15,000,000
Amortization of Regulatory Asset																																																																																											77,000,000																						116,000,000	12,000,000
Finite Lived Intangible Assets Future Amortization Expense [Abstract]
Future amortization expense within the next twelve months	29,000,000									29,000,000																																																																																	118,000,000																			19,000,000	24,000,000			75,000,000	[1]
Future amortization expense in year two	29,000,000									29,000,000																																																																																	60,000,000																			18,000,000	24,000,000			18,000,000	[1]
Future amortizationExpense in year three	29,000,000									29,000,000																																																																																	11,000,000																			18,000,000	24,000,000			(31,000,000)	[1]
Future amortization expense in year four	29,000,000									29,000,000																																																																																	21,000,000																			18,000,000	24,000,000			(21,000,000)	[1]
Future amortization expense in year five	29,000,000									29,000,000																																																																																	53,000,000																			18,000,000	24,000,000			11,000,000	[1]
Future amortization expense in year six and thereafter																																																																																											233,000,000																			87,000,000	77,000,000			69,000,000	[1]
Procurement Construction Contract [Abstract]
Capital Expenditures										(38,000,000)	160,000,000		96,000,000																		(107,000,000)	[2]	103,000,000	[3]	125,000,000																	(8,000,000)	15,000,000		7,000,000													13,000,000	26,000,000		(35,000,000)											(48,000,000)	(4,000,000)		(7,000,000)
Business Combination, Description [Abstract]
Business Acquisitions, Megawatts Acquired																																																																																																								720				230
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination, Integration Related Costs																																																																																											142,000,000	804,000,000			106,000,000	340,000,000	16,000,000	41,000,000	9,000,000	17,000,000	6,000,000	182,000,000
Payments To Acquire Businesses Net Of Cash Acquired [Abstract]
Payments To Acquire Businesses Gross											21,000,000		387,000,000																		0		21,000,000		387,000,000																																																																				305,000,000		75,000,000
Total fair value of consideration recorded																																																																																																							311,000,000		75,000,000
BusinessAcquisitionPreexistingRelationshipGainLossRecognized																																																																																																							6,000,000
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Net Abstract
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Property Plant And Equipment					9,342,000,000						9,342,000,000															4,054,000,000							4,054,000,000																																																																						347,000,000		15,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory																																																																																																							5,000,000
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Intangibles																																																																																																									190,000,000	[4]
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Asset Retirment Obligations					740,000,000						740,000,000
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Working Capital																																																																																																							(5,000,000)		5,000,000
Expected Investment In Equity																																																																																																											650,000,000
DOE loan guarantee																															646,000,000																																																																												646,000,000
Amount of solar panels																																																																																																											3,800,000
Amount of homes powered by electricity generated																																																																																																											75,000
Purchased Power agreement time																																																																																																											25 years
Footnotes To Business Combination Recognized Identifiable Assets Acquired Liabilities Assumed Net [Abstract]
First Solar Corporation Payable																																																																																																											87,000,000		135,000,000
Current Assets					4,936,000,000						4,936,000,000															3,638,000,000							3,638,000,000
Unamortized Energy Contracts					3,218,000,000						3,218,000,000															3,218,000,000							3,218,000,000
Other intangibles, trade name and retail relationships					457,000,000						457,000,000															457,000,000							457,000,000
Investment in affiliates					1,942,000,000						1,942,000,000															1,942,000,000							1,942,000,000
Other assets					2,265,000,000						2,265,000,000															1,266,000,000							1,266,000,000
Total assets					22,900,000,000						22,900,000,000															14,575,000,000							14,575,000,000
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract
Current liabilities					3,408,000,000						3,408,000,000															2,804,000,000							2,804,000,000
Unamortized energy contracts					1,722,000,000						1,722,000,000															1,512,000,000							1,512,000,000																																																																								(135,000,000)	[5]
Long-term debt, including current maturities					5,632,000,000						5,632,000,000															2,972,000,000							2,972,000,000
Business Combination Aquisition Of Less than 100 Percent Noncontrolling Interest Fair Value					90,000,000						90,000,000															90,000,000							90,000,000
Deferred credits and other liabilities and preferred securities					4,683,000,000						4,683,000,000															1,933,000,000							1,933,000,000
Total liabilities,preferred securities and noncontrolling Interest					15,535,000,000						15,535,000,000															9,311,000,000							9,311,000,000
Total purchase price					7,365,000,000						7,365,000,000															5,264,000,000							5,264,000,000																																																																						347,000,000		75,000,000
Business Combination, Bargain Purchase [Abstract]
Business Combination, Bargain Purchase, Gain Recognized, Amount													36,000,000																						36,000,000																																																																				36,000,000
Business Acquisition, Impact Of Merger [Abstract]
Revenues	6,163,000,000	6,502,000,000	6,141,000,000	6,082,000,000	6,254,000,000		6,579,000,000	5,966,000,000	4,690,000,000	24,888,000,000	23,489,000,000		19,063,000,000									3,772,000,000	4,255,000,000	4,070,000,000	3,533,000,000	3,898,000,000		4,031,000,000	3,765,000,000	2,743,000,000	15,630,000,000		14,437,000,000		10,447,000,000								1,068,000,000	1,156,000,000	1,080,000,000	1,160,000,000	1,290,000,000		1,484,000,000	1,281,000,000	1,388,000,000	4,464,000,000	5,443,000,000		6,056,000,000				805,000,000	728,000,000	672,000,000	895,000,000	790,000,000		806,000,000	715,000,000	875,000,000	3,100,000,000	3,186,000,000		3,720,000,000		794,000,000	737,000,000	653,000,000	880,000,000	703,000,000		720,000,000	616,000,000	697,000,000	3,065,000,000	2,735,000,000		3,068,000,000					2,091,000,000
Revenues Impact
Net Income Loss Impact																																																																																		(31,000,000)	(31,000,000)
Net income	495,000,000	738,000,000	490,000,000	(4,000,000)	378,000,000		296,000,000	286,000,000	200,000,000	1,729,000,000	1,171,000,000		2,499,000,000									269,000,000	490,000,000	330,000,000	(18,000,000)	137,000,000		91,000,000	166,000,000	168,000,000	1,060,000,000		558,000,000		1,771,000,000								109,000,000	126,000,000	96,000,000	(81,000,000)	160,000,000		90,000,000	42,000,000	87,000,000	249,000,000	379,000,000		416,000,000				102,000,000	92,000,000	72,000,000	121,000,000	79,000,000		122,000,000	79,000,000	96,000,000	395,000,000	381,000,000		389,000,000		47,000,000	50,000,000	22,000,000	77,000,000	15,000,000		(4,000,000)	13,000,000	(33,000,000)	210,000,000	4,000,000		136,000,000
Regulatory Assets Transfer Changes										17,000,000																																										11,000,000																															8,000,000			6,000,000	6,000,000					58,000,000						36,000,000				22,000,000
Business Acquisition, Pro Forma Information [Abstract]
Business Acquisition, Pro Forma Revenue										26,700,000,000	30,712,000,000	[6]																			17,013,000,000		19,494,000,000	[7]
Business Acquisition, Pro Forma Net Income (Loss)										2,092,000,000	974,000,000	[6]																			1,205,000,000		324,000,000	[7]
Business Acquisition, Pro Forma Earnings Per Share, Basic										$ 2.56	$ 1.15	[6]
Business Acquisition, Pro Forma Earnings Per Share, Diluted										$ 2.55	$ 1.14	[6]
Business Acquisition, Pro Forma Nonrecurring Cost													236,000,000																						203,000,000
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, Construction Time Frame																				1 year	2 years
Business Acquisition, Development Of New Generation Cost																					650,000,000																																																																						600,000,000
Business Acquisition, Expected New Generation Mwh																				285	300
Business Acquisition, Expected New Generation Development Time Frame										10 years
Business Acquisition, Divesture Wattage																																																																																											2,648
Business Acquisition, Divesture Sales Days										150 days
Business Acquisition, Divesture Sales Days Extension										30 days
Business Acquisition, Proceeds Assets Held For Sale																																																																																													371,000,000
Business Acquisition Potential Cash Payment	40,000,000									40,000,000
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Start				111,000,000						111,000,000															33,000,000						33,000,000															1,000,000						1,000,000																								11,000,000						11,000,000
Severance Charges											124,000,000	[8]		5,000,000	124,000,000		18,000,000	19,000,000	5,000,000														80,000,000	[8]		1,000,000	38,000,000			16,000,000	14,000,000	5,000,000											14,000,000	[8],[9]		2,000,000	2,000,000	2,000,000											7,000,000	[8]		1,000,000											17,000,000	[8],[9]			11,000,000	3,000,000	4,000,000
Non-Merger Severance Costs										0	99,000,000																				0		34,000,000
Stock Compensation Expense											7,000,000	[8]																					4,000,000	[8]					2,000,000														1,000,000	[8],[9]																													1,000,000	[8],[9]
Other Expense Charges					7,000,000	[8]					7,000,000	[8]						7,000,000								4,000,000	[8]						4,000,000	[8]							2,000,000						1,000,000	[8],[9]					1,000,000	[8],[9]																							1,000,000	[8],[9]					1,000,000	[8],[9]				1,000,000
Total Severance Benefits					138,000,000	[8]					138,000,000	[8]														88,000,000	[8]						88,000,000	[8]													16,000,000	[8],[9]					16,000,000	[8],[9]									7,000,000	[8]					7,000,000	[8]							19,000,000	[8],[9]					19,000,000	[8],[9]
Restructuring Reserve, Period Expense																3,000,000																						1,000,000
Payments										64,000,000	27,000,000																				24,000,000		9,000,000																			1,000,000	1,000,000																													5,000,000	1,000,000
Restructuring Reserve, Intercompany Allocation																															5,000,000
Restructuring Reserve, Period End	53,000,000				111,000,000					53,000,000	111,000,000											10,000,000				33,000,000					10,000,000		33,000,000										0				1,000,000					0	1,000,000																				6,000,000				11,000,000					6,000,000	11,000,000
Business Acquisition, Costs Recognized Post Merger [Abstract]
BGE rate credit of $100 per residential customer											113,000,000	[10]																																																																							113,000,000	[10]
Customer investment fund to invest in energy efficiency and low-income energy assistance to BGE customers											113,500,000
Contribution for renewable energy, energy efficiency or related projects in Baltimore											2,000,000
Charitable contributions at $7 million per year for 10 years											70,000,000																						35,000,000																																																		28,000,000
State funding for offshore wind development projects											32,000,000
Miscellaneous tax benefits											(2,000,000)																																																																								(2,000,000)
Total											$ 328,500,000																						$ 35,000,000																																																		$ 139,000,000
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Business Acquisition, Equity Interest Issued Or Issuable, Stock Withheld																																																																																														0.7

[1] Includes the fair value of BGE's power and gas supply contracts of $12 million for which an offsetting Exelon Corporate regulatory asset was also recorded. (b) Weighted average amortization period was calculated as of the date of acquisition.

[2] Includes $55 million of changes in capital expenditures not paid between December 31, 2013 and 2012 related to Antelope Valley.

[3] Includes $127 million of changes in capital expenditures not paid between December 31, 2012 and 2011 related to Antelope Valley.

[4] See Note 10 - Intangible Assets for additional information.

[5] Generation concluded that the remaining, yet-to-be paid $135 million in consideration was embedded in the amounts payable under the Engineering, Procurement, Construction (EPC) agreement for First Solar, Inc. to construct the solar facility. For accounting purposes, this aspect of the transaction is considered to be akin to a "seller financing" arrangement. As such, Generation recorded a liability of $135 million associated with the portion of the future payments to First Solar, Inc. under the EPC agreement to reflect Generation's implicit amounts due First Solar, Inc. for the remainder of the value of the net assets acquired. The $135 million payable to First Solar, Inc. will be relieved as Generation makes payments for costs incurred over the project construction period. At December 31, 2012, $87 million remained payable to First Solar, Inc. During 2013, a subsidiary of Generation paid off the remaining balance of the payable to First Solar, Inc.

[6] The amounts above include non-recurring costs directly related to the merger of $236 million for the year ended December 31, 2011.

[7] The amounts above include non-recurring costs directly related to the merger of $203 million for the year ended December 31, 2011.

[8] The amounts above include $46 million at Generation, $14 million at ComEd, $7 million at PECO, and $7 million at BGE, for amounts billed by BSC through intercompany allocations for the year ended December 31, 2013.

[9] Exelon, ComEd and BGE established regulatory assets of $35 million, $16 million and $19 million, respectively, for severance benefits costs for the year ended December 31, 2012. The majority of these costs are expected to be recovered over a five-year period.

[10] Exelon made a $66 million equity contribution to BGE in the second quarter of 2012 to fund the after-tax amount of the rate credit as directed in the MDPSC order approving the merger transaction.