Severance and Plant Retirements (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended		6 Months Ended							6 Months Ended		6 Months Ended							6 Months Ended		6 Months Ended								6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 CENGMember [Member]	Jun. 30, 2014 Severance [Member]	Dec. 31, 2013 Severance [Member]	Jun. 30, 2014 Severance [Member] CENGMember [Member]	Dec. 31, 2013 Severance [Member] CENGMember [Member]	Jun. 30, 2014 Other Severance Charges [Member]	Jun. 30, 2013 Other Severance Charges [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] CENGMember [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Severance [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member] Severance [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Severance [Member] CENGMember [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member] Severance [Member] CENGMember [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Other Severance Charges [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Other Severance Charges [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] CENGMember [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Severance [Member] CENGMember [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Severance [Member] CENGMember [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Other Severance Charges [Member]	Jun. 30, 2014 PECO Energy Co [Member]	Jun. 30, 2013 PECO Energy Co [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] CENGMember [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] Severance [Member] CENGMember [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Severance [Member] CENGMember [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	$ 4	$ 1						$ 6	$ 2	$ 2	$ 1						$ 4	$ 1	$ 0	$ 0				$ 1	$ 0	$ 0	$ 0	$ 0
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Start				20	2	33	53						20	2	8	10						0	0							3	6
Severance Charges	2		19							2		19
Non-Merger Severance Costs												6
Payments	3		20							3		2									0								3
Restructuring Reserve, Period End				20	2	33	53						20	2	8	10						0	0							3	6
Business Acquisition, Costs Recognized Post Merger [Abstract]
Business Acquisition Charitable Contributions Per Year	7
Plant Retirement Cost [Abstract]
Inventory write down related to plant retirements	$ 3									$ 3									$ 1