Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Capitalized Interest And AFUDC [Line Items]
Total interest incurred			$ 1,003,000,000	[1]	$ 783,000,000	[1]
Capitalized interest	54,000,000		67,000,000		49,000,000
Credits to AFUDC debt and equity	35,000,000		25,000,000		25,000,000
Capitalized Software [Line Items]
Net unamortized software costs	479,000,000		499,000,000
Amortization of capitalized software costs	198,000,000		208,000,000		122,000,000
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Operating and maintenance	7,270,000,000		7,961,000,000		5,184,000,000
Interest Expense	1,315,000,000		891,000,000		701,000,000
Consolidation Percentages Detail Tagging [Abstract]
Percentage ownership of consolidated subsidiaries	100.00%
Percentage ownership of common stock	100.00%
Minimum voting interest needed for a controlling financial interest	50.00%
Third Party interest in ComEd	15,000,000		106,000,000
Cost Method Investment Ownership Percentage	20.00%
New Site Development Costs [Abstract]
Capitalized development costs	1,900,000,000		1,200,000,000
Development costs expensed	4,000,000		4,000,000		2,000,000
Minimum [Member]
Consolidation Percentages Detail Tagging [Abstract]
Equity Method Investment Ownership Percentage	20.00%
Maximum [Member]
Consolidation Percentages Detail Tagging [Abstract]
Equity Method Investment Ownership Percentage	50.00%
Commonwealth Edison Company [Member]
Consolidation Percentages Detail Tagging [Abstract]
Percentage ownership of consolidated subsidiaries	99.00%
Third Party interest in ComEd	1,000,000
Exelon SHC Inc [Member]
Consolidation Percentages Detail Tagging [Abstract]
Minority Interest Ownership Percentage By Parent	1.00%
CENG [Member]
Consolidation Percentages Detail Tagging [Abstract]
Equity Method Investment Ownership Percentage	50.01%
RITELine Illinois LLC [Member]
Consolidation Percentages Detail Tagging [Abstract]
Minority Interest Ownership Percentage By Parent	12.50%
Third-party percentage interest in subsidaries	12.50%
Third Party interest in ComEd	1,000,000
Exelon Generation Co L L C [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred	411,000,000	[1]	368,000,000	[1]	219,000,000	[1]
Capitalized interest	54,000,000		67,000,000		49,000,000
Capitalized Software [Line Items]
Net unamortized software costs	129,000,000		143,000,000
Amortization of capitalized software costs	67,000,000		81,000,000		41,000,000
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Operating and maintenance	3,960,000,000		4,398,000,000		2,827,000,000
Interest Expense	298,000,000		226,000,000		170,000,000
Consolidation Percentages Detail Tagging [Abstract]
Percentage ownership of consolidated subsidiaries	100.00%
Equity Method Investment Ownership Percentage	50.01%
Ownership Interest Upper Bound	99.00%
Ownership Interest Lower Bound	94.00%
Third Party interest in ComEd	17,000,000		108,000,000
New Site Development Costs [Abstract]
Capitalized development costs	1,900,000,000		1,200,000,000
Development costs expensed	4,000,000		4,000,000		2,000,000
Nuclear Fuel [Abstract]
Cost of spent nuclear fuel disposal per kWh of net nuclear generation	0.001
Exelon Generation Co L L C [Member] | Minimum [Member]
Consolidation Percentages Detail Tagging [Abstract]
Third-party percentage interest in subsidaries	1.00%
Exelon Generation Co L L C [Member] | Maximum [Member]
Consolidation Percentages Detail Tagging [Abstract]
Third-party percentage interest in subsidaries	6.00%
Exelon Generation Co L L C [Member] | Exelon SHC Inc [Member]
Consolidation Percentages Detail Tagging [Abstract]
Percentage ownership of consolidated subsidiaries	99.00%
Commonwealth Edison Co [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred	584,000,000	[1]	310,000,000	[1]	349,000,000	[1]
Credits to AFUDC debt and equity	16,000,000		9,000,000		12,000,000
Capitalized Software [Line Items]
Net unamortized software costs	101,000,000		105,000,000
Amortization of capitalized software costs	52,000,000		56,000,000		50,000,000
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Electrical transmission and distribution revenue	4,461,000,000		5,441,000,000		6,054,000,000
Operating and maintenance	1,211,000,000		1,182,000,000		1,031,000,000
Interest Expense	566,000,000		294,000,000		330,000,000
Consolidation Percentages Detail Tagging [Abstract]
Percentage ownership of consolidated subsidiaries	100.00%
Commonwealth Edison Co [Member] | RITELine Illinois LLC [Member]
Consolidation Percentages Detail Tagging [Abstract]
Percentage ownership of consolidated subsidiaries	75.00%
Third-party percentage interest in subsidaries	25.00%
Third Party interest in ComEd	1,000,000
PECO Energy Co [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred	117,000,000	[1]	125,000,000	[1]	138,000,000	[1]
Credits to AFUDC debt and equity	6,000,000		6,000,000		13,000,000
Capitalized Software [Line Items]
Net unamortized software costs	71,000,000		63,000,000
Amortization of capitalized software costs	33,000,000		30,000,000		25,000,000
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Operating and maintenance	647,000,000		698,000,000		698,000,000
Interest Expense	103,000,000		111,000,000		122,000,000
Baltimore Gas and Electric Company [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred	129,000,000	[1]	149,000,000	[1]	136,000,000	[1]
Credits to AFUDC debt and equity	13,000,000		15,000,000		22,000,000
Capitalized Software [Line Items]
Net unamortized software costs	155,000,000		157,000,000
Amortization of capitalized software costs	36,000,000		32,000,000		25,000,000
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Operating and maintenance	551,000,000		622,000,000		530,000,000
Interest Expense	106,000,000		128,000,000		113,000,000
Baltimore Gas and Electric Company [Member] | Scenario Adjustment [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Electrical transmission and distribution revenue	2,000,000
Operating and maintenance	3,000,000
Interest Expense	$ 5,000,000

[1] Exelon activity for the year ended December 31, 2012 includes the results of Constellation and BGE for March 12, 2012 – December 31, 2012. Generation activity for the year ended December 31, 2012 includes the results of Constellation for March 12, 2012 – December 31, 2012. BGE activity represents the activity for the years ended December 31, 2012, 2011 and 2010. (b)        Includes interest expense to affiliates.