Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Current assets	$ 550.00	[1]	$ 15.00
Noncurrent assets	1,802.00	[1]	784.00
Total Assets	2,352.00	[1]	799.00
Current liabilities	685.00	[1]	181.00
Noncurrent liabilities	837.00	[1]	77.00
Total Liabilities	1,522.00	[1]	258.00
Variable Interest Entity Nonconsolidated Carrying Amount Assets Liabilities And Other Information [Abstract]
Total assets	740.00	[2]
Total liabilities	333.00	[2]
Our ownership interest	97.00	[2]
Other ownership interests	310.00	[2]
Letter of Credit [Member]
Variable Interest Entity Nonconsolidated Carrying Amount Assets Liabilities And Other Information [Abstract]
Other ownership interests	5.00
Investments [Member]
Variable Interest Entity Nonconsolidated Carrying Amount Assets Liabilities And Other Information [Abstract]
Other ownership interests	77.00
Payment Guarantee [Member]
Variable Interest Entity Nonconsolidated Carrying Amount Assets Liabilities And Other Information [Abstract]
Other ownership interests	5.00
Exelon Generation Co L L C [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Current assets	519.00		15.00
Noncurrent assets	1,762.00		784.00
Total Assets	2,281.00		799.00
Current liabilities	613.00		181.00
Noncurrent liabilities	532.00		77.00
Total Liabilities	1,145.00		258.00
Exelon Generation Co L L C [Member] | Solar Project Limited Liability Companies [Member]
Consolidated Variable Interest Entity [Abstract]
Ownership percentage, consolidated variable interest entity (as a percent)	100.00%
Baltimore Gas and Electric Company [Member]
Consolidated Variable Interest Entity [Abstract]
Remittance of payments received from customers for rate stabilization to BondCo.	85.00		92.00		90.00
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Current assets	30.00	[3]	30.00	[3]
Noncurrent assets	0	[3]	0	[3]
Total Assets	30.00	[3]	30.00	[3]
Current liabilities	71.00	[3]	69.00	[3]
Noncurrent liabilities	265.00	[3]	332.00	[3]
Total Liabilities	$ 336.00	[3]	$ 401.00	[3]

[1] Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity.

[2] These items represent amounts on the unconsolidated VIE balance sheets, not on Exelon’s or Generation’s Consolidated Balance Sheets. These items are included to provide information regarding the relative size of the unconsolidated VIEs.

[3] Amounts related to BGE are presented for the standalone entity as of both December 31, 2012 and 2011.