Commitments and Contingencies - Litigation and Regulatory Matters (Details) (USD $)	12 Months Ended	9 Months Ended		0 Months Ended	9 Months Ended		9 Months Ended
	Dec. 31, 2013	Sep. 30, 2014 Exelon Generation Co L L C [Member] Open_claim	Dec. 31, 2013 Exelon Generation Co L L C [Member]	Jul. 11, 2011 Commonwealth Edison Co [Member] Customer	Sep. 30, 2014 Commonwealth Edison Co [Member] claimant Customer	Jun. 05, 2013 Commonwealth Edison Co [Member] Customer	Sep. 30, 2014 Commonwealth Edison Co [Member] Maximum [Member]	Sep. 30, 2014 Commonwealth Edison Co [Member] Minimum [Member]	Sep. 30, 2014 Baltimore Gas and Electric Company [Member] claimant
Asbestos Loss Contingency [Abstract]
Asbestos liability reserve		$ 103,000,000	$ 90,000,000
Asbestos liability reserve related to open claims		22,000,000
Open asbestos liability claims		265
Asbestos liability reserve related to anticipated claims		81,000,000
Increase (decrease) in the value of the asbestos liability reserve	25,000,000	15,000,000
Number of claimants									486
Continuous Power Interruption [Abstract]
Minimum number of customers ComEd can be held liable to for power interruption					30,000
Number of customers affected by a major storm				900,000
Number of customers proposed by the ICC that ComEd should not be granted a waiver under Continuous Power Interruption						34,559
Telephone Consumer Protection Act Lawsuit [Abstract]
Possible Defendants Number					1,200,000
Loss Contingency, Damages Sought, Value							$ 1,500	$ 500