Fair Value of Financial Assets and Liabilities (Fair Value By Balance Sheet Grouping) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Long-term debt to financing trusts	$ 648	$ 648
Carrying Reported Amount Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	344	214
Long-term debt (including amounts due within one year)	19,132	18,745
Long-term debt to financing trusts	648	648
Spent nuclear fuel obligation	1,021	1,020
Preferred securities of subsidiary		87
Estimate Of Fair Value Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities		214
Long-term debt (including amounts due within one year)		20,520
Long-term debt to financing trusts		664
Spent nuclear fuel obligation		763
Preferred securities of subsidiary	0	82
Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 1 [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	3
Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 2 [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	341
Long-term debt (including amounts due within one year)	18,672
Spent nuclear fuel obligation	790
Preferred securities of subsidiary	0
Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 3 [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,079
Long-term debt to financing trusts	631
Exelon Generation Co L L C [Member] | Carrying Reported Amount Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	22	0
Long-term debt (including amounts due within one year)	7,729	7,483
Spent nuclear fuel obligation	1,021	1,020
Exelon Generation Co L L C [Member] | Estimate Of Fair Value Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities		0
Long-term debt (including amounts due within one year)		7,849
Spent nuclear fuel obligation		763
Exelon Generation Co L L C [Member] | Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 2 [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	22
Long-term debt (including amounts due within one year)	6,586
Spent nuclear fuel obligation	790
Exelon Generation Co L L C [Member] | Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 3 [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,062
Commonwealth Edison Co [Member] | Carrying Reported Amount Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	184
Long-term debt (including amounts due within one year)	5,675	5,567
Long-term debt to financing trusts	206	206
Commonwealth Edison Co [Member] | Estimate Of Fair Value Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)		6,548
Long-term debt to financing trusts		212
Commonwealth Edison Co [Member] | Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 2 [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	184
Long-term debt (including amounts due within one year)	6,238
Commonwealth Edison Co [Member] | Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 3 [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	17
Long-term debt to financing trusts	202
PECO Energy Co [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Long-term debt to financing trusts	184	184
PECO Energy Co [Member] | Carrying Reported Amount Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	0	210
Long-term debt (including amounts due within one year)	2,197	1,947
Long-term debt to financing trusts	184	184
Preferred securities of subsidiary	0	87
PECO Energy Co [Member] | Estimate Of Fair Value Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities		210
Long-term debt (including amounts due within one year)		2,264
Long-term debt to financing trusts		188
Preferred securities of subsidiary		82
PECO Energy Co [Member] | Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 2 [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	0
Long-term debt (including amounts due within one year)	2,358
Preferred securities of subsidiary	0
PECO Energy Co [Member] | Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 3 [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Long-term debt to financing trusts	180
Baltimore Gas and Electric Company [Member] | Carrying Reported Amount Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	138
Long-term debt (including amounts due within one year)	2,011	2,178
Long-term debt to financing trusts	258	258
Baltimore Gas and Electric Company [Member] | Estimate Of Fair Value Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)		2,468
Long-term debt to financing trusts		263
Baltimore Gas and Electric Company [Member] | Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 1 [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	3
Baltimore Gas and Electric Company [Member] | Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 2 [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	135
Long-term debt (including amounts due within one year)	2,148
Baltimore Gas and Electric Company [Member] | Estimate Of Fair Value Fair Value Disclosure [Member] | Fair Value Inputs Level 3 [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Long-term debt to financing trusts	$ 249