Changes in Accumulated Other Comprehensive Income (Reclassification out of Accumulated Other Comprehensive Income)(Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	$ 6,163	$ 6,502	$ 6,141	$ 6,082	$ 6,254	$ 6,579	$ 5,966	$ 4,690	$ 24,888		$ 23,489	$ 19,063
Interest Expense									1,315		891	701
Other income and deductions									(883)		(582)	(523)
Income before income taxes									2,773		1,798	3,956
Income taxes									1,044		627	1,457
Net income (loss)	495	738	490	(4)	378	296	286	200	1,729		1,171	2,499
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit PlansTax [Abstract]
Prior service costs											1	(4)
Transition obligation											2	2
Loss on equity method investments									10		(91)	(1)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other income and deductions									461	[1]
Income taxes									(184)	[1]
Net income (loss)									64	[1]
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit PlansTax [Abstract]
Deferred compensation unit									(1)	[1],[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]
Net income (loss)									277	[1]
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]
Other income and deductions									464	[1]
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]
Other income and deductions									(3)	[1]
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit PlansTax [Abstract]
Prior service costs									(2)	[1],[3]
Actuarial gains/losses									(339)	[1],[3]
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Pension Plans Defined Benefit [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes									(342)	[1]
Income taxes									134	[1]
Net income (loss)									(208)	[1]
Equity Method Investments | Reclassification out of Accumulated Other Comprehensive Income [Member] | Other Equity Investment Reclassified Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues									(8)	[1]
Income before income taxes									(8)	[1]
Income taxes									3	[1]
Net income (loss)									(5)	[1]
Exelon Generation Co L L C [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	3,772	4,255	4,070	3,533	3,898	4,031	3,765	2,743	15,630		14,437	10,447
Interest Expense									298		226	170
Other income and deductions									11		(62)	(48)
Income before income taxes									1,675		1,058	2,827
Income taxes									615		500	1,056
Net income (loss)	269	490	330	(18)	137	91	166	168	1,060		558	1,771
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit PlansTax [Abstract]
Loss on equity method investments									10		(91)	(1)
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]
Other income and deductions									683	[1]
Net income (loss)									408	[1]
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income taxes									(270)	[1]
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]
Net income (loss)									413	[1]
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]
Other income and deductions									683	[1]
Exelon Generation Co L L C [Member] | Equity Method Investments | Reclassification out of Accumulated Other Comprehensive Income [Member] | Other Equity Investment Reclassified Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues									(8)	[1]
Income before income taxes									(8)	[1]
Income taxes									3	[1]
Net income (loss)									(5)	[1]
Commonwealth Edison Co [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	1,068	1,156	1,080	1,160	1,290	1,484	1,281	1,388	4,464		5,443	6,056
Interest Expense									566		294	330
Other income and deductions									(553)		(268)	(316)
Income before income taxes									401		618	666
Income taxes									152		239	250
Net income (loss)	109	126	96	(81)	160	90	42	87	249		379	416
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit PlansTax [Abstract]
Loss on equity method investments									0		0	0
PECO Energy Co [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	805	728	672	895	790	806	715	875	3,100		3,186	3,720
Interest Expense									103		111	122
Other income and deductions									(109)		(115)	(120)
Income before income taxes									557		508	535
Income taxes									162		127	146
Net income (loss)	102	92	72	121	79	122	79	96	395		381	389
Baltimore Gas and Electric Company [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	794	737	653	880	703	720	616	697	3,065		2,735	3,068
Interest Expense									106		128	113
Other income and deductions									(105)		(121)	(103)
Income before income taxes									344		11	211
Income taxes									134		7	75
Net income (loss)	$ 47	$ 50	$ 22	$ 77	$ 15	$ (4)	$ 13	$ (33)	$ 210		$ 4	$ 136

[1] Amounts in parenthesis represent a decrease in net income.

[2] Amortization of the deferred compensation unit plan is allocated to capital and operating and maintenance expense.

[3] This accumulated other comprehensive income component is included in the computation of net periodic pension and OPEB cost (see note 16 for additional details).