Property, Plant and Equipment (Details) (USD $)	Mar. 31, 2012		Dec. 31, 2011
Property Plant And Equipment [Line Items]
Less: accumulated depreciation	$ 11,244,000,000	[1]	$ 10,959,000,000	[2]
Property, plant and equipment, net	42,105,000,000		32,570,000,000
Exelon Generation Co L L C [Member]
Property Plant And Equipment [Line Items]
Less: accumulated depreciation	5,563,000,000	[1]	5,313,000,000	[2]
Property, plant and equipment, net	17,480,000,000		13,475,000,000
Commonwealth Edison Co [Member]
Property Plant And Equipment [Line Items]
Less: accumulated depreciation	2,769,000,000		2,750,000,000
Property, plant and equipment, net	13,267,000,000		13,121,000,000
PECO Energy Co [Member]
Property Plant And Equipment [Line Items]
Less: accumulated depreciation	2,691,000,000		2,662,000,000
Property, plant and equipment, net	5,924,000,000		5,874,000,000
Baltimore Gas and Electric Company [Member]
Property Plant And Equipment [Line Items]
Less: accumulated depreciation	2,508,000,000		2,465,000,000
Property, plant and equipment, net	$ 5,211,000,000		$ 5,132,000,000

[1] Includes accumulated amortization of nuclear fuel in the reactor core of $1,851 million.

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