Debt and Credit Agreements - Summary of Credit Facility Thresholds (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Nov. 24, 2014	Jan. 09, 2015
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 1,190	[1]
Credit facility threshold	2.50 to 1
Credit facility threshold	2.50
Exelon Generation Co L L C [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	1,181	[1]
Credit facility threshold	3.00 to 1
Credit facility threshold	3.00
Commonwealth Edison Co [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	2	[1]
Credit facility threshold	2.00 to 1
Credit facility threshold	2.00
PECO Energy Co [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	1	[1]
Credit facility threshold	2.00 to 1
Credit facility threshold	2.00
Baltimore Gas and Electric Company [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	0	[1]
Credit facility threshold	2.00 to 1
Credit facility threshold	2.00
citibank Bank [Member] | Exelon Generation Co L L C [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount			25
CIBC Bank [Member] | Exelon Generation Co L L C [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount				$ 75

[1] Excludes nonrecourse debt letters of credit, see discussion below on Continental Wind.