Property, Plant and Equipment (Details) (USD $)	Sep. 30, 2012		Dec. 31, 2011
Property Plant And Equipment [Line Items]
Less: accumulated depreciation	$ (11,890,000,000)	[1]	$ (10,959,000,000)	[2]
Property, plant and equipment, net	43,914,000,000		32,570,000,000
Property Plant And Equipment Footnotes [Abstract]
Accumulated amortization of nuclear fuel	2,161,000,000		1,784,000,000
Exelon Generation Co L L C [Member]
Property Plant And Equipment [Line Items]
Less: accumulated depreciation	(5,910,000,000)	[1]	(5,313,000,000)	[2]
Property, plant and equipment, net	18,708,000,000		13,475,000,000
Property Plant And Equipment Footnotes [Abstract]
Accumulated amortization of nuclear fuel	2,161,000,000		1,784,000,000
Commonwealth Edison Co [Member]
Property Plant And Equipment [Line Items]
Less: accumulated depreciation	(2,906,000,000)		(2,750,000,000)
Property, plant and equipment, net	13,611,000,000		13,121,000,000
PECO Energy Co [Member]
Property Plant And Equipment [Line Items]
Less: accumulated depreciation	(2,765,000,000)		(2,662,000,000)
Property, plant and equipment, net	5,996,000,000		5,874,000,000
Baltimore Gas and Electric Company [Member]
Property Plant And Equipment [Line Items]
Less: accumulated depreciation	(2,579,000,000)		(2,465,000,000)
Property, plant and equipment, net	$ 5,378,000,000		$ 5,132,000,000

[1] Includes accumulated amortization of nuclear fuel in the reactor core of $2,161 million.

[2] Includes accumulated amortization of nuclear fuel in the reactor core of $1,784 million.