Debt and Credit Agreements - Summary of Credit Facility Thresholds (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 1,478	[1]
Credit agreement threshold	2.50 to 1
Credit agreement threshold	2.50
Exelon Generation Co L L C [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 1,449	[1]
Credit agreement threshold	3.00 to 1
Credit agreement threshold	3.00
Commonwealth Edison Co [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 2	[1]
Credit agreement threshold	2.00 to 1
Credit agreement threshold	2.00
PECO Energy Co [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 1	[1]
Credit agreement threshold	2.00 to 1
Credit agreement threshold	2.00
Baltimore Gas and Electric Company [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 0	[1]
Credit agreement threshold	2.00 to 1
Credit agreement threshold	2.00

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