Significant Accounting Policies (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Operating and maintenance	$ 1,858,000,000	$ 1,764,000,000
Interest Expense	217,000,000	617,000,000
Consolidation Percentages Detail Tagging [Abstract]
Third Party interest in ComEd	17,000,000		15,000,000
Exelon Generation Co L L C [Member]
Operating and maintenance	938,000,000	965,000,000
Interest Expense	73,000,000	65,000,000
Consolidation Percentages Detail Tagging [Abstract]
Equity Method Investment Ownership Percentage	50.01%
Third Party interest in ComEd	19,000,000		17,000,000
Nuclear Fuel [Abstract]
Cost of spent nuclear fuel disposal per kWh of net nuclear generation	0.001
Commonwealth Edison Co [Member]
Electrical transmission and distribution revenue	1,133,000,000	1,159,000,000
Operating and maintenance	287,000,000	292,000,000
Interest Expense	77,000,000	350,000,000
PECO Energy Co [Member]
Operating and maintenance	256,000,000	164,000,000
Interest Expense	25,000,000	26,000,000
Baltimore Gas and Electric Company [Member]
Operating and maintenance	163,000,000	124,000,000
Interest Expense	$ 23,000,000	$ 29,000,000