Changes in Accumulated Other Comprehensive Income (Reclassification out of Accumulated Other Comprehensive Income)(Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	$ 7,237	[1]	$ 6,082	[1]
Interest Expense	217		617
Other income and deductions	(124)		(451)
Income before income taxes	39		57
Income taxes	(54)		56
Net income (loss)	93		1
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit PlansTax [Abstract]
Prior service costs	(1)		0
Loss on equity method investments	(19)		(9)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	(12)	[2]	6	[2]
Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	39	[2]	98	[2]
Income taxes	(15)	[2]	(40)	[2]
Net income (loss)	24	[2]
Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Energy Related Derivative [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	39	[2]	99	[2]
Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Interest Expense			(1)	[2]
Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivative [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income taxes			58	[2]
Accumulated Defined Benefit Plans Adjustment [Member]
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit PlansTax [Abstract]
Prior service costs	(2)	[3]
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	(58)	[2]	(83)	[2]
Income taxes	23	[2]	33	[2]
Net income (loss)	(35)	[2]	(50)	[2]
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit PlansTax [Abstract]
Deferred compensation unit	0	[2]
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Pension Plans Defined Benefit [Member]
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit PlansTax [Abstract]
Actuarial gains/losses	(56)	[2]	(83)	[2]
Equity Method Investments | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	(1)		(3)	[2]
Income taxes	0		1	[2]
Net income (loss)	(1)		(2)	[2]
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit PlansTax [Abstract]
Loss on equity method investments			(3)	[2]
Exelon Generation Co L L C [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	4,390		3,533
Interest Expense	73		65
Other income and deductions	5		46
Income before income taxes	(384)		(18)
Income taxes	(199)		(1)
Net income (loss)	(185)		(17)
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit PlansTax [Abstract]
Loss on equity method investments	(19)		(9)
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	23	[2]	133	[2]
Exelon Generation Co L L C [Member] | Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	39	[2]	223	[2]
Income taxes	(15)	[2]	(88)	[2]
Net income (loss)	24	[2]
Exelon Generation Co L L C [Member] | Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Energy Related Derivative [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	39	[2]	223	[2]
Exelon Generation Co L L C [Member] | Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Interest Expense			0
Exelon Generation Co L L C [Member] | Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivative [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income taxes			135	[2]
Exelon Generation Co L L C [Member] | Equity Method Investments | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	(1)		(3)	[2]
Income taxes	0		1	[2]
Net income (loss)	(1)		(2)	[2]
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit PlansTax [Abstract]
Loss on equity method investments	(1)		(3)	[2]
Commonwealth Edison Co [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	1,134		1,160
Interest Expense	77		350
Other income and deductions	(75)		(348)
Income before income taxes	163		(139)
Income taxes	65		(58)
Net income (loss)	98		(81)
PECO Energy Co [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	993		895
Interest Expense	25		26
Other income and deductions	(26)		(26)
Income before income taxes	123		177
Income taxes	34		55
Net income (loss)	89		122
Baltimore Gas and Electric Company [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	1,054		880
Interest Expense	23		29
Other income and deductions	(23)		(28)
Income before income taxes	146		135
Income taxes	58		55
Net income (loss)	$ 88		$ 80

[1] For the ##D<curmonth> months ended ##D<cyperiod> and ##D<pyfiscal>, utility taxes of $##D<gcytdutiltax> million and $##D<gpytdutiltax> million, respectively, are included in revenues and expenses for Generation. For the ##D<curmonth> months ended ##D<cyperiod> and ##D<pyfiscal>, utility taxes of $##D<ccytdutiltax> million and $##D<cpytdutiltax> million, respectively, are included in revenues and expenses for ComEd. For the ##D<curmonth> months ended ##D<cyperiod> and ##D<pyfiscal>, utility taxes of $##D<pcytdutiltax> million and $##D<ppytdutiltax> million, respectively, are included in revenues and expenses for PECO. For the ##D<curmonth> months ended ##D<cyperiod> and period of March 12, 2012 through ##D<pyperiod>, utility taxes of $##D<bcytdutiltax> million and $##D<bpytdutiltax> million, respectively, are included in revenues and expenses for BGE.

[2] (a) All amounts are net of tax. Amounts in parenthesis represent a decrease in net income.

[3] (a) All amounts are net of tax. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.