Jointly Owned Electric Utility Plant (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Exelon Generation Co L L C [Member] | Nuclear Generation [Member] | Quad Cities [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Operator	Generation
Plant	$ 941	[1]	$ 874	[1]
Accumulated depreciation	226	[1]	187	[1]
Construction work in progress	27		44
Jointly Owned Utility Plant Footnote [Abstract]
Plant	941	[1]	874	[1]
Exelon Generation Co L L C [Member] | Nuclear Generation [Member] | Peach Bottom [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Operator	Generation
Plant	883	[1]	796	[1]
Accumulated depreciation	326	[1]	302	[1]
Construction work in progress	174		115
Jointly Owned Utility Plant Footnote [Abstract]
Plant	883	[1]	796	[1]
Exelon Generation Co L L C [Member] | Nuclear Generation [Member] | Salem [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Operator	PSEG Nuclear	[2]
Ownership interest	42.59%
Plant	501	[1],[2]	494	[1],[2]
Accumulated depreciation	134	[1],[2]	119	[1],[2]
Construction work in progress	24	[2]	11	[2]
Jointly Owned Utility Plant Footnote [Abstract]
Ownership interest	42.59%
Plant	501	[1],[2]	494	[1],[2]
Exelon Generation Co L L C [Member] | Fossil Fuel Generation [Member] | Salem [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Plant	3		3
Jointly Owned Utility Plant Footnote [Abstract]
Plant	3		3
Exelon Generation Co L L C [Member] | Fossil Fuel Generation [Member] | Keystone [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Operator	GenOn	[3]
Plant	725	[1],[3]	624	[1],[3]
Accumulated depreciation	268	[1],[3]	153	[1],[3]
Construction work in progress	6	[3]	10	[3]
Jointly Owned Utility Plant Footnote [Abstract]
Plant	725	[1],[3]	624	[1],[3]
Exelon Generation Co L L C [Member] | Fossil Fuel Generation [Member] | Conemaugh [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Operator	GenOn	[3]
Plant	399	[1],[3]	322	[1],[3]
Accumulated depreciation	220	[1],[3]	158	[1],[3]
Construction work in progress	121	[3]	57	[3]
Jointly Owned Utility Plant Footnote [Abstract]
Plant	399	[1],[3]	322	[1],[3]
Exelon Generation Co L L C [Member] | Fossil Fuel Generation [Member] | Wyman [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Operator	FP&L
Plant	3	[1]	3	[1]
Accumulated depreciation	3	[1]	3	[1]
Construction work in progress	0		0
Jointly Owned Utility Plant Footnote [Abstract]
Plant	3	[1]	3	[1]
Exelon Generation Co L L C [Member] | Other Service [Member] | Other Locations [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Operator		[4]
Plant	2	[1],[4]	1	[1],[4]
Accumulated depreciation	1	[1],[4]	0	[1],[4]
Construction work in progress	0	[4]	0	[4]
Jointly Owned Utility Plant Footnote [Abstract]
Plant	2	[1],[4]	1	[1],[4]
PECO Energy Co [Member] | Electric Transmission [Member] | Pennsylvania [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Operator	First Energy	[5]
Plant	14	[1],[5]	13	[1],[5]
Accumulated depreciation	7	[1],[5]	7	[1],[5]
Construction work in progress	0	[5]	1	[5]
Jointly Owned Utility Plant Footnote [Abstract]
Plant	14	[1],[5]	13	[1],[5]
Miles of transmission voltage lines	127
Transmission line capacity	500
PECO Energy Co [Member] | Electric Transmission [Member] | Delaware And New Jersey [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Operator	PSEG	[6]
Plant	64	[1],[6]	65	[1],[6]
Accumulated depreciation	34	[1],[6]	33	[1],[6]
Construction work in progress	0	[6]	0	[6]
Jointly Owned Utility Plant Footnote [Abstract]
Plant	$ 64	[1],[6]	$ 65	[1],[6]
Miles of transmission voltage lines	131
Transmission line capacity	500
PECO Energy Co [Member] | Electric Transmission [Member] | PA Transmission Lines [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest	22.00%
Jointly Owned Utility Plant Footnote [Abstract]
Ownership interest	22.00%
PECO Energy Co [Member] | Electric Transmission [Member] | Conemaugh Substation [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest	20.70%
Jointly Owned Utility Plant Footnote [Abstract]
Ownership interest	20.70%
Transmission line capacity	500
Substation capacity	500
Baltimore Gas and Electric Company [Member] | Conemaugh Substation [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest	10.56%
Jointly Owned Utility Plant Footnote [Abstract]
Ownership interest	10.56%
Baltimore Gas and Electric Company [Member] | Electric Transmission [Member] | Pennsylvania [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest	7.00%
Jointly Owned Utility Plant Footnote [Abstract]
Ownership interest	7.00%

[1] Excludes asset retirement costs.

[2]         Generation also owns a proportionate share in the fossil fuel combustion turbine at Salem, which is fully depreciated. The gross book value was $3 million at December 31, 2013 and 2012.

[3] Generation’s ownership interest in Keystone and Conemaugh has increased as a result of Exelon’s merger with Constellation in 2012. See Note 4 – Merger and Acquisitions for additional information.

[4] Generation has a 44.24% ownership interest in Merrill Creek Reservoir located in New Jersey.

[5] PECO and BGE own a 22% and 7% share, respectively, in 127 miles of 500 kV lines located in Pennsylvania; PECO and BGE also own a 20.7% and 10.56% share, respectively, of a 500 kV substation immediately outside of the Conemaugh fossil generating station which supplies power to the 500 kV lines including, but not limited to, the lines noted above.

[6] PECO owns a 42.55% share in 131 miles of 500 kV lines located in Delaware and New Jersey as well as a 42.55% share in a 500kV substation immediately outside of the Salem nuclear generating station in New Jersey which supplies power to the 500kV lines including, but not limited to, the lines noted above.