Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Operating and maintenance	$ 1,735	$ 2,170	$ 5,391	$ 5,979
Interest Expense	228	240	1,091	678
Exelon Generation Co L L C [Member]
Operating and maintenance	936	1,289	2,943	3,319
Interest Expense	82	85	257	223
Consolidation Percentages Detail Tagging [Abstract]
Exelon Percentage ownership of Exelon SHC, LLC	50.01%		50.01%
Commonwealth Edison Co [Member]
Electrical transmission and distribution revenue	1,155	1,484	3,393	4,152
Operating and maintenance	296	313	907	882
Interest Expense	71	71	493	221
PECO Energy Co [Member]
Operating and maintenance	162	172	480	491
Interest Expense	26	29	77	85
Baltimore Gas and Electric Company [Member]
Operating and maintenance	125	172	391	460
Interest Expense	29	35	94	110
Baltimore Gas and Electric Company [Member] | Scenario Adjustment [Member]
Operating and maintenance			$ 4