Property, Plant and Equipment (Details) (USD $)																																																																							12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2012 Electric Transmission And Distribution [Member]	Dec. 31, 2011 Electric Transmission And Distribution [Member]	Dec. 31, 2012 Electric Generation Equipment [Member]		Dec. 31, 2011 Electric Generation Equipment [Member]		Dec. 31, 2012 Gas Distribution Equipment [Member]	Dec. 31, 2011 Gas Distribution Equipment [Member]	Dec. 31, 2012 Common Electric And Gas T And D Equipment [Member]	Dec. 31, 2011 Common Electric And Gas T And D Equipment [Member]	Dec. 31, 2012 Nuclear Fuel [Member]		Dec. 31, 2011 Nuclear Fuel [Member]		Dec. 31, 2012 Public Utilities Property Plant And Equipment Construction Work In Progress [Member]	Dec. 31, 2011 Public Utilities Property Plant And Equipment Construction Work In Progress [Member]	Dec. 31, 2012 Other Capitalized Property Plant And Equipment [Member]		Dec. 31, 2011 Other Capitalized Property Plant And Equipment [Member]		Dec. 31, 2012 Exelon Generation Co L L C [Member]		Dec. 31, 2011 Exelon Generation Co L L C [Member]		Dec. 31, 2012 Exelon Generation Co L L C [Member] Electric Generation Equipment [Member]		Dec. 31, 2011 Exelon Generation Co L L C [Member] Electric Generation Equipment [Member]		Dec. 31, 2012 Exelon Generation Co L L C [Member] Nuclear Fuel [Member]		Dec. 31, 2011 Exelon Generation Co L L C [Member] Nuclear Fuel [Member]		Dec. 31, 2012 Exelon Generation Co L L C [Member] Public Utilities Property Plant And Equipment Construction Work In Progress [Member]	Dec. 31, 2011 Exelon Generation Co L L C [Member] Public Utilities Property Plant And Equipment Construction Work In Progress [Member]	Dec. 31, 2012 Exelon Generation Co L L C [Member] Other Capitalized Property Plant And Equipment [Member]		Dec. 31, 2011 Exelon Generation Co L L C [Member] Other Capitalized Property Plant And Equipment [Member]		Dec. 31, 2012 Commonwealth Edison Co [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Electric Transmission And Distribution [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Electric Transmission And Distribution [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Public Utilities Property Plant And Equipment Construction Work In Progress [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Public Utilities Property Plant And Equipment Construction Work In Progress [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Other Capitalized Property Plant And Equipment [Member]		Dec. 31, 2011 Commonwealth Edison Co [Member] Other Capitalized Property Plant And Equipment [Member]		Dec. 31, 2012 PECO Energy Co [Member]	Dec. 31, 2011 PECO Energy Co [Member]	Dec. 31, 2012 PECO Energy Co [Member] Electric Transmission And Distribution [Member]	Dec. 31, 2011 PECO Energy Co [Member] Electric Transmission And Distribution [Member]	Dec. 31, 2012 PECO Energy Co [Member] Gas Distribution Equipment [Member]	Dec. 31, 2011 PECO Energy Co [Member] Gas Distribution Equipment [Member]	Dec. 31, 2012 PECO Energy Co [Member] Common Electric And Gas T And D Equipment [Member]	Dec. 31, 2011 PECO Energy Co [Member] Common Electric And Gas T And D Equipment [Member]	Dec. 31, 2012 PECO Energy Co [Member] Public Utilities Property Plant And Equipment Construction Work In Progress [Member]	Dec. 31, 2011 PECO Energy Co [Member] Public Utilities Property Plant And Equipment Construction Work In Progress [Member]	Dec. 31, 2012 PECO Energy Co [Member] Other Capitalized Property Plant And Equipment [Member]		Dec. 31, 2011 PECO Energy Co [Member] Other Capitalized Property Plant And Equipment [Member]		Dec. 31, 2012 Baltimore Gas and Electric Company [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Electric Transmission And Distribution [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Electric Transmission And Distribution [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Electric Transmission And Distribution [Member] Minimum [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Electric Transmission And Distribution [Member] Maximum [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Gas Distribution Equipment [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Gas Distribution Equipment [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Gas Distribution Equipment [Member] Minimum [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Gas Distribution Equipment [Member] Maximum [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Common Electric And Gas T And D Equipment [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Common Electric And Gas T And D Equipment [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Common Electric And Gas T And D Equipment [Member] Minimum [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Common Electric And Gas T And D Equipment [Member] Maximum [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Public Utilities Property Plant And Equipment Construction Work In Progress [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Public Utilities Property Plant And Equipment Construction Work In Progress [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Other Capitalized Property Plant And Equipment [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Other Capitalized Property Plant And Equipment [Member]	Dec. 31, 2012 Electric Transmission And Distribution [Member]	Dec. 31, 2011 Electric Transmission And Distribution [Member]	Dec. 31, 2010 Electric Transmission And Distribution [Member]	Dec. 31, 2011 Electric Transmission And Distribution [Member] Commonwealth Edison Co [Member]	Dec. 31, 2010 Electric Transmission And Distribution [Member] Commonwealth Edison Co [Member]	Dec. 31, 2012 Electric Transmission And Distribution [Member] PECO Energy Co [Member]	Dec. 31, 2011 Electric Transmission And Distribution [Member] PECO Energy Co [Member]	Dec. 31, 2010 Electric Transmission And Distribution [Member] PECO Energy Co [Member]	Dec. 31, 2012 Electric Transmission And Distribution [Member] Baltimore Gas and Electric Company [Member]	Dec. 31, 2011 Electric Transmission And Distribution [Member] Baltimore Gas and Electric Company [Member]	Dec. 31, 2010 Electric Transmission And Distribution [Member] Baltimore Gas and Electric Company [Member]	Dec. 31, 2012 Electric Generation Equipment [Member]	Dec. 31, 2011 Electric Generation Equipment [Member]	Dec. 31, 2010 Electric Generation Equipment [Member]	Dec. 31, 2011 Electric Generation Equipment [Member] Exelon Generation Co L L C [Member]	Dec. 31, 2010 Electric Generation Equipment [Member] Exelon Generation Co L L C [Member]	Dec. 31, 2012 Gas Distribution Equipment [Member]	Dec. 31, 2011 Gas Distribution Equipment [Member]	Dec. 31, 2010 Gas Distribution Equipment [Member]	Dec. 31, 2012 Gas Distribution Equipment [Member] PECO Energy Co [Member]	Dec. 31, 2011 Gas Distribution Equipment [Member] PECO Energy Co [Member]	Dec. 31, 2010 Gas Distribution Equipment [Member] PECO Energy Co [Member]	Dec. 31, 2012 Gas Distribution Equipment [Member] Baltimore Gas and Electric Company [Member]	Dec. 31, 2011 Gas Distribution Equipment [Member] Baltimore Gas and Electric Company [Member]	Dec. 31, 2010 Gas Distribution Equipment [Member] Baltimore Gas and Electric Company [Member]	Dec. 31, 2012 Common Electric And Gas T And D Equipment [Member]	Dec. 31, 2011 Common Electric And Gas T And D Equipment [Member]	Dec. 31, 2010 Common Electric And Gas T And D Equipment [Member]	Dec. 31, 2012 Common Electric And Gas T And D Equipment [Member] PECO Energy Co [Member]	Dec. 31, 2011 Common Electric And Gas T And D Equipment [Member] PECO Energy Co [Member]	Dec. 31, 2010 Common Electric And Gas T And D Equipment [Member] PECO Energy Co [Member]	Dec. 31, 2012 Common Electric And Gas T And D Equipment [Member] Baltimore Gas and Electric Company [Member]	Dec. 31, 2011 Common Electric And Gas T And D Equipment [Member] Baltimore Gas and Electric Company [Member]	Dec. 31, 2010 Common Electric And Gas T And D Equipment [Member] Baltimore Gas and Electric Company [Member]
Property Plant And Equipment Average Service Life Percentage By Asset Category [Line Items]
Annual depreciation rate																																																																																					2.76%	2.59%	2.53%	2.67%	2.64%	2.51%	2.33%	2.17%	2.92%	2.89%	2.88%	3.15%	3.12%	2.86%	3.12%	2.86%	2.03%	1.73%	1.75%	1.77%	1.73%	1.75%	2.33%	2.41%	2.42%	7.61%	8.05%	7.25%	7.54%	8.05%	7.25%	7.68%	8.40%	7.24%
Property Plant And Equipment [Line Items]
Total property, plant and equipment	$ 57,370,000,000		$ 43,529,000,000		$ 26,576,000,000	$ 21,716,000,000	$ 19,004,000,000	[1]	$ 13,682,000,000	[1]	$ 3,108,000,000	$ 1,793,000,000	$ 1,029,000,000	$ 564,000,000	$ 4,815,000,000	[2]	$ 4,225,000,000	[2]	$ 1,926,000,000	$ 1,110,000,000	$ 912,000,000	[3]	$ 439,000,000	[3]	$ 25,545,000,000		$ 18,788,000,000		$ 19,004,000,000	[1]	$ 13,682,000,000	[1]	$ 4,815,000,000	[2]	$ 4,225,000,000	[2]	$ 1,352,000,000	$ 827,000,000	$ 374,000,000	[4]	$ 54,000,000	[4]	$ 16,824,000,000	$ 15,871,000,000	$ 16,480,000,000	$ 15,637,000,000	$ 294,000,000	$ 187,000,000	$ 50,000,000	[5]	$ 47,000,000	[5]	$ 8,875,000,000	$ 8,536,000,000	$ 6,355,000,000	$ 6,079,000,000	$ 1,859,000,000	$ 1,793,000,000	$ 568,000,000	$ 564,000,000	$ 76,000,000	$ 83,000,000	$ 17,000,000	[5]	$ 17,000,000	[5]	$ 8,093,000,000	$ 7,598,000,000	$ 5,767,000,000	$ 5,483,000,000			$ 1,548,000,000	$ 1,387,000,000			$ 554,000,000	$ 415,000,000			$ 193,000,000	$ 298,000,000	$ 31,000,000	$ 15,000,000
Less: accumulated depreciation	(12,184,000,000)	[6]	(10,959,000,000)	[6]																					(6,014,000,000)	[7]	(5,313,000,000)	[7]															(2,998,000,000)	(2,750,000,000)									(2,797,000,000)	(2,662,000,000)													(2,595,000,000)	(2,466,000,000)
Property, plant and equipment, net	45,186,000,000		32,570,000,000																						19,531,000,000		13,475,000,000																13,826,000,000	13,121,000,000									6,078,000,000	5,874,000,000													5,498,000,000	5,132,000,000
Property, plant and equipment, useful life																																																																							5 years	90 years			5 years	90 years			5 years	50 years			20 years
Property Plant And Equipment Footnotes [Abstract]
Nuclear fuel - work in progress			6,000,000																								674
Buildings under capital lease	2,000,000		2,000,000																						2,000,000		23,000,000
Original cost basis for buildings	53,000,000																								53,000,000
Accumulated depreciation for buildings	3,000,000																										30,000,000
Accumulated amortization of nuclear fuel	$ 2,078,000,000		$ 1,000,000																								$ 1,784,000,000

[1] Includes assets acquired through acquisitions. See Note 4 – Mergers and Acquisitions for additional information.

[2] Includes nuclear fuel that is in the fabrication and installation phase of $894 million and $674 million at December 31, 2012 and 2011, respectively.

[3] Includes Generation's buildings under capital lease with a net carrying value of $20 million and $23 million at December 31, 2012 and 2011, respectively. The original cost basis of the buildings was $53 million and total accumulated amortization was $33 million and $30 million as of December 31, 2012 and 2011, respectively. Also includes land held for future use and non utility property at ComEd, PECO and BGE. These balances also include capitalized acquisition, development and exploration costs related to oil and gas production activities at Generation.

[4] Includes buildings under capital lease with a net carrying value of $20 million and $23 million at December 31, 2012 and 2011, respectively. The original cost basis of the buildings was $53 million and total accumulated amortization was $33 million and $30 million as of December 31, 2012 and 2011, respectively.

[5] Represents land held for future use and non utility property.

[6] Includes accumulated amortization of nuclear fuel in the reactor core at Generation of $2,078 million and $1,784 million as of December 31, 2012 and 2011, respectively.

[7] Includes accumulated amortization of nuclear fuel in the reactor core of $2,078 million and $1,784 million as of December 31, 2012 and 2011, respectively.