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Derivative Financial Instruments (Commodity Price Risk) (Details)
3 Months Ended 6 Months Ended
Jun. 30, 2013
GWh
Jun. 30, 2012
GWh
Jun. 30, 2013
GWh
Exelon Generation Co L L C [Member]
     
Proprietary Trading Volumes [Abstract]      
Proprietary trading activities volume 1,995 4,248 3,567
Exelon Generation Co L L C [Member] | Minimum [Member]
     
Percent Of Expected Generation Being Hedged [Abstract]      
Expected generation hedged in next twelve months     96.00%
Expected generation hedged in year two     78.00%
Expected generation hedged in year three     41.00%
Exelon Generation Co L L C [Member] | Maximum [Member]
     
Percent Of Expected Generation Being Hedged [Abstract]      
Expected generation hedged in next twelve months     99.00%
Expected generation hedged in year two     81.00%
Expected generation hedged in year three     44.00%
PECO Energy Co [Member]
     
Percent Of Gas Purchases Being Hedged [Abstract]      
Estimated percentage of natural gas purchases hedged     30.00%
Baltimore Gas and Electric Company [Member] | Minimum [Member]
     
Percent Of Gas Purchases Being Hedged [Abstract]      
Estimated percentage of natural gas purchases hedged     10.00%
Baltimore Gas and Electric Company [Member] | Maximum [Member]
     
Percent Of Gas Purchases Being Hedged [Abstract]      
Estimated percentage of natural gas purchases hedged     20.00%