Changes in Accumulated Other Comprehensive Income (Changes in accumulated other comprehensive income by component)(Details) (USD $) In Millions, unless otherwise specified	3 Months Ended																																									3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Mar. 31, 2014 Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member]		Mar. 31, 2013 Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member]		Mar. 31, 2014 Accumulated Net Unrealized Investment Gain Loss [Member]		Mar. 31, 2013 Accumulated Net Unrealized Investment Gain Loss [Member]		Mar. 31, 2014 Accumulated Defined Benefit Plans Adjustment [Member]		Mar. 31, 2013 Accumulated Defined Benefit Plans Adjustment [Member]		Mar. 31, 2014 Accumulated Translation Adjustment [Member]		Mar. 31, 2013 Accumulated Translation Adjustment [Member]		Mar. 31, 2014 Accumulated Equity Investment [Member]		Mar. 31, 2013 Accumulated Equity Investment [Member]		Mar. 31, 2014 Accumulated Other Comprehensive (Loss) Income, Net	Mar. 31, 2014 Exelon Generation Co L L C [Member]		Mar. 31, 2013 Exelon Generation Co L L C [Member]		Mar. 31, 2014 Exelon Generation Co L L C [Member] Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member]		Mar. 31, 2013 Exelon Generation Co L L C [Member] Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member]		Mar. 31, 2014 Exelon Generation Co L L C [Member] Accumulated Net Unrealized Investment Gain Loss [Member]		Mar. 31, 2013 Exelon Generation Co L L C [Member] Accumulated Net Unrealized Investment Gain Loss [Member]		Mar. 31, 2013 Exelon Generation Co L L C [Member] Accumulated Defined Benefit Plans Adjustment [Member]		Dec. 31, 2012 Exelon Generation Co L L C [Member] Accumulated Defined Benefit Plans Adjustment [Member]		Mar. 31, 2014 Exelon Generation Co L L C [Member] Accumulated Translation Adjustment [Member]		Mar. 31, 2013 Exelon Generation Co L L C [Member] Accumulated Translation Adjustment [Member]		Mar. 31, 2014 Exelon Generation Co L L C [Member] Accumulated Equity Investment [Member]		Mar. 31, 2013 Exelon Generation Co L L C [Member] Accumulated Equity Investment [Member]		Mar. 31, 2014 Exelon Generation Co L L C [Member] Accumulated Other Comprehensive (Loss) Income, Net	Mar. 31, 2014 Commonwealth Edison Co [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member]	Mar. 31, 2014 PECO Energy Co [Member]		Dec. 31, 2013 PECO Energy Co [Member]		Mar. 31, 2013 PECO Energy Co [Member]		Dec. 31, 2012 PECO Energy Co [Member]		Mar. 31, 2014 PECO Energy Co [Member] Accumulated Net Unrealized Investment Gain Loss [Member]		Dec. 31, 2013 PECO Energy Co [Member] Accumulated Net Unrealized Investment Gain Loss [Member]		Mar. 31, 2013 PECO Energy Co [Member] Accumulated Net Unrealized Investment Gain Loss [Member]		Dec. 31, 2012 PECO Energy Co [Member] Accumulated Net Unrealized Investment Gain Loss [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	$ (2,040)	[1]	$ (2,767)	[1]	$ 120	[1]	$ 368	[1]	$ 2	[1]			$ (2,260)	[1]	$ (3,137)	[1]	$ (10)	[1]			$ 108	[1]	$ 2	[1]		$ 214	[1]	$ 513	[1]	$ 114	[1]	$ 513	[1]	$ 2	[1]	$ (1)	[1]	$ (19)	[1]	$ (19)	[1]	$ (10)	[1]			$ 108	[1]	$ 20	[1]		$ 0	$ 0	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]
OCI before reclassifications	(8)	[1]	100	[1]	(1)	[1]			0	[1]	(1)	[1]	(13)	[1]	76	[1]	(5)	[1]	(1)	[1]	11	[1]	26	[1]		2	[1]	29	[1]	(1)	[1]	5	[1]	(3)	[1]	(1)	[1]					(5)	[1]	(1)	[1]	11	[1]	26	[1]
Amounts reclassified from AOCI	12	[1],[2]	(6)	[1],[3]	(24)	[1],[2]	(58)	[1],[3]					35	[1],[2]	50	[1],[3]					1	[1],[2]	2	[1],[3]		(23)	[1],[2]	(133)	[1],[3]	(24)	[1],[2]	(135)	[1],[3]													1	[1],[2]	2	[1],[3]
Net current-period OCI	4	[1]	94	[1]	(25)	[1]	(58)	[1]	0	[1]	(1)	[1]	22	[1]	126	[1]	(5)	[1]	(1)	[1]	12	[1]	28	[1]		(21)	[1]	(104)	[1]	(25)	[1]	(130)	[1]	(3)	[1]	(1)	[1]					(5)	[1]	(1)	[1]	12	[1]	28	[1]	(21)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(2,036)	[1]	(2,673)	[1]	95	[1]	310	[1]	2	[1]	(1)	[1]	(2,238)	[1]	(3,011)	[1]	(15)	[1]	(1)	[1]	120	[1]	30	[1]		193	[1]	409	[1]	89	[1]	383	[1]	(1)	[1]	(2)	[1]	(19)	[1]	(19)	[1]	(15)	[1]	(1)	[1]	120	[1]	48	[1]		0	0	1	[1]	1	[1]	1	[1]	1	[1]	1	[1]	1	[1]	1	[1]	1	[1]
OtherComprehensiveIncomeLossTaxParentheticalDisclosuresAbstract
Prior service costs	(1)		0										(2)	[1]
Actuarial loss reclassified to periodic cost, taxes	23		32
Pension and non-pension postretirement benefit plan valuation adjustment, taxes	(7)		49
Change in unrealized gain (loss) on cash flow hedges, taxes	18		33																							19		86
Change in unrealized gain (loss) on marketable securities, taxes																										(2)
Change in unrealized gain (loss) on equity investments taxes	(7)		(18)																		(1)					(7)		(18)
Other comprehensive income, income taxes	$ (6)		$ (66)																						$ 6	$ 10		$ 68																						$ 10

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

[2] (b) This accumulated other comprehensive income component is included in the computation of net periodic pension and OPEB cost (see Note 11 for additional details).

[3] (b) See tables following changes in accumulated other comprehensive income tables for details about these reclassifications.