Stock-Based Compensation Plans (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013		Dec. 31, 2013
Common Stock [Abstract]
Common Stock without par - Authorized	2,000,000,000				2,000,000,000				2,000,000,000
Common Stock without par - Outstanding	893,940,600				893,940,600				857,000,000
Share Based Compensation Components [Abstract]
Stock-based compensation costs					$ 68		$ 70
Other stock-based awards	1		1		4		3
Total stock-based compensation included in operating and maintenance expense	27		20		97		89
Income Tax Benefit	(10)		(8)		(37)		(34)
Total after-tax stock based compensation expense	17		12		60		55
Share Based Compensation Pre Tax Expense [Line Items]
Pre-tax stock based compensation expense	27		20		97		89
Exelon Generation Co L L C [Member]
Share Based Compensation Components [Abstract]
Stock-based compensation costs					0		0
Share Based Compensation Pre Tax Expense [Line Items]
Pre-tax stock based compensation expense	10		9		38		33
Commonwealth Edison Co [Member]
Share Based Compensation Components [Abstract]
Stock-based compensation costs					0		0
Share Based Compensation Pre Tax Expense [Line Items]
Pre-tax stock based compensation expense	3		2		7		9
PECO Energy Co [Member]
Share Based Compensation Components [Abstract]
Stock-based compensation costs					0		0
Share Based Compensation Pre Tax Expense [Line Items]
Pre-tax stock based compensation expense	1		1		4		4
Baltimore Gas and Electric Company [Member]
Share Based Compensation Components [Abstract]
Stock-based compensation costs					0		0
Share Based Compensation Pre Tax Expense [Line Items]
Pre-tax stock based compensation expense	1	[1]	1	[1]	5	[1]	4	[1]
Business Services Company [Member]
Share Based Compensation Pre Tax Expense [Line Items]
Pre-tax stock based compensation expense	$ 12	[2]	$ 7	[2]	$ 43	[2]	$ 39	[2]

[1] BGE's stock-based compensation expense (pre-tax) for the six months ended June 30, 2013 excludes $2 million of cost incurred in 2012 prior to the closing of Exelon's merger with Constellation on March 12, 2012. This amount is not included in Exelon's stock-based compensation expense for the six months ended June 30, 2013 shown in the tables titled Components of Stock-Based Compensation Expense and Subsidiaries above.

[2] These amounts primarily represent amounts billed to Exelon's subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO and BGE amounts above.