Commitments and Contingencies - Litigation and Regulatory Matters (Details)		3 Months Ended	6 Months Ended
	Jul. 11, 2011 Customer	Jun. 30, 2015 USD ($) claimant Open_claim	Jun. 30, 2015 USD ($) Customer claimant Open_claim	Dec. 31, 2014 USD ($)	Jun. 05, 2013 Customer
Exelon Generation Co L L C [Member]
Asbestos Loss Contingency [Abstract]
Asbestos liability reserve		$ 97,000,000	$ 97,000,000	$ 100,000,000
Asbestos liability reserve related to open claims		$ 20,000,000	$ 20,000,000
Open asbestos liability claims | Open_claim		213	213
Asbestos liability reserve related to anticipated claims		$ 77,000,000	$ 77,000,000
Increase (decrease) in the value of the asbestos liability reserve		1,000,000
Commonwealth Edison Co [Member]
Continuous Power Interruption [Abstract]
Minimum number of customers ComEd can be held liable to for power interruption | Customer			30,000
Number of customers affected by a major storm | Customer	900,000
Number of customers proposed by the ICC that ComEd should not be granted a waiver under Continuous Power Interruption | Customer					34,559
Telephone Consumer Protection Act Lawsuit [Abstract]
Possible Defendants Number | claimant			1,200,000
Commonwealth Edison Co [Member] | Legal Reserve [Member]
Telephone Consumer Protection Act Lawsuit [Abstract]
Accrued Liabilities		$ 5,000,000	$ 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 | claimant		468	468