Commitments and Contingencies - Litigation and Regulatory Matters (Details) (USD $)	0 Months Ended	3 Months Ended
	Jul. 11, 2011 Customer	Mar. 31, 2015 claimant Customer	Dec. 31, 2014	Jun. 05, 2013 Customer
Exelon Generation Co L L C [Member]
Asbestos Loss Contingency [Abstract]
Asbestos liability reserve		97,000,000	$ 100,000,000
Asbestos liability reserve related to open claims		20,000,000
Open asbestos liability claims		224
Asbestos liability reserve related to anticipated claims		77,000,000
Commonwealth Edison Co [Member]
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
Commonwealth Edison Co [Member] | Legal Reserve [Member]
Telephone Consumer Protection Act Lawsuit [Abstract]
Accrued Liabilities		5,000,000
Commonwealth Edison Co [Member] | Maximum [Member]
Telephone Consumer Protection Act Lawsuit [Abstract]
Loss Contingency, Damages Sought, Value		1,500
Commonwealth Edison Co [Member] | Minimum [Member]
Telephone Consumer Protection Act Lawsuit [Abstract]
Loss Contingency, Damages Sought, Value		500
Baltimore Gas and Electric Company [Member]
Asbestos Loss Contingency [Abstract]
Number of claimants		467