Fair Value of Financial Assets and Liabilities (Fair Value By Balance Sheet Grouping) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Carrying Reported Amount Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	$ 624	$ 344
Long-term debt (including amounts due within one year)	20,180	19,132
Long-term debt to financing trusts	648	648
Spent nuclear fuel obligation	1,021	1,021
Preferred securities of subsidiary		0
Estimate Of Fair Value Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	624	344
Long-term debt (including amounts due within one year)	21,658	19,751
Long-term debt to financing trusts	668	631
Spent nuclear fuel obligation	814	790
Preferred securities of subsidiary		0
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	3
Long-term debt (including amounts due within one year)	1,150
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	621	341
Long-term debt (including amounts due within one year)	19,373	18,672
Spent nuclear fuel obligation	814	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)	1,135	1,079
Long-term debt to financing trusts	668	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	53	22
Long-term debt (including amounts due within one year)	7,507	7,729
Spent nuclear fuel obligation	1,021	1,021
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	53	22
Long-term debt (including amounts due within one year)	8,016	7,648
Spent nuclear fuel obligation	814	790
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	53	22
Long-term debt (including amounts due within one year)	6,881	6,586
Spent nuclear fuel obligation	814	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)	1,135	1,062
Commonwealth Edison Co [Member] | Carrying Reported Amount Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	498	184
Long-term debt (including amounts due within one year)	5,708	5,675
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]
Short-term liabilities	498	184
Long-term debt (including amounts due within one year)	6,452	6,255
Long-term debt to financing trusts	211	202
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	498	184
Long-term debt (including amounts due within one year)	6,452	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)	0	17
Long-term debt to financing trusts	211	202
PECO Energy Co [Member] | Carrying Reported Amount Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	0	0
Long-term debt (including amounts due within one year)	2,197	2,197
Long-term debt to financing trusts	184	184
PECO Energy Co [Member] | Estimate Of Fair Value Fair Value Disclosure [Member]
Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract]
Short-term liabilities	0	0
Long-term debt (including amounts due within one year)	2,436	2,358
Long-term debt to financing trusts	198	180
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	0
Long-term debt (including amounts due within one year)	2,436	2,358
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	198	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	73	138
Long-term debt (including amounts due within one year)	1,976	2,011
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]
Short-term liabilities	73	138
Long-term debt (including amounts due within one year)	2,206	2,148
Long-term debt to financing trusts	259	249
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	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	70	135
Long-term debt (including amounts due within one year)	2,206	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	$ 259	$ 249