Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended																								3 Months Ended				9 Months Ended																9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]		Sep. 30, 2013 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]		Sep. 30, 2014 Accumulated Net Unrealized Investment Gain (Loss) [Member]		Sep. 30, 2013 Accumulated Net Unrealized Investment Gain (Loss) [Member]		Sep. 30, 2014 Accumulated Defined Benefit Plans Adjustment [Member]		Sep. 30, 2013 Accumulated Defined Benefit Plans Adjustment [Member]		Sep. 30, 2014 Accumulated Translation Adjustment [Member]		Sep. 30, 2013 Accumulated Translation Adjustment [Member]		Sep. 30, 2014 Accumulated Equity Investment [Member]		Sep. 30, 2013 Accumulated Equity Investment [Member]		Sep. 30, 2014 Exelon Generation Co L L C [Member]		Sep. 30, 2013 Exelon Generation Co L L C [Member]		Sep. 30, 2014 Exelon Generation Co L L C [Member]		Sep. 30, 2013 Exelon Generation Co L L C [Member]		Sep. 30, 2014 Exelon Generation Co L L C [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]		Sep. 30, 2013 Exelon Generation Co L L C [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]		Sep. 30, 2014 Exelon Generation Co L L C [Member] Accumulated Net Unrealized Investment Gain (Loss) [Member]		Sep. 30, 2013 Exelon Generation Co L L C [Member] Accumulated Net Unrealized Investment Gain (Loss) [Member]		Sep. 30, 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]		Sep. 30, 2014 Exelon Generation Co L L C [Member] Accumulated Translation Adjustment [Member]		Sep. 30, 2013 Exelon Generation Co L L C [Member] Accumulated Translation Adjustment [Member]		Sep. 30, 2014 Exelon Generation Co L L C [Member] Accumulated Equity Investment [Member]		Sep. 30, 2013 Exelon Generation Co L L C [Member] Accumulated Equity Investment [Member]		Sep. 30, 2014 PECO Energy Co [Member]		Dec. 31, 2013 PECO Energy Co [Member]		Sep. 30, 2013 PECO Energy Co [Member]		Dec. 31, 2012 PECO Energy Co [Member]		Sep. 30, 2014 PECO Energy Co [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]		Dec. 31, 2013 PECO Energy Co [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]		Sep. 30, 2013 PECO Energy Co [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]		Dec. 31, 2012 PECO Energy Co [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]		Sep. 30, 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]		Sep. 30, 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]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
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]	$ 512	[1]	$ 2	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ (10)	[1]			$ 108	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]
OCI before reclassifications					229	[1]	138	[1]	(14)	[1]	25	[1]	(2)	[1]	(1)	[1]	240	[1]	73	[1]	(6)	[1]	(5)	[1]	11	[1]	46	[1]					(6)	[1]	53	[1]	(8)	[1]	12	[1]	(3)	[1]	(1)	[1]					(6)	[1]	(5)	[1]	11	[1]	47	[1]
Amounts reclassified from AOCI					(106)	[1],[2]	(32)	[1],[2]	(78)	[1],[2]	(194)	[1],[2]					91	[1],[2]	157	[1],[2]					(119)	[1],[2]	5	[1],[2]					(197)	[1],[2]	(323)	[1],[2]	(78)	[1],[2]	(328)	[1],[2]													(119)	[1],[2]	5	[1],[2]
Net current-period OCI	(11)		12		123	[1]	106	[1]	(92)	[1]	(169)	[1]	(2)	[1]	(1)	[1]	331	[1]	230	[1]	(6)	[1]	(5)	[1]	(108)	[1]	51	[1]	(26)		(32)		(203)	[1]	(270)	[1]	(86)	[1]	(316)	[1]	(3)	[1]	(1)	[1]					(6)	[1]	(5)	[1]	(108)	[1]	52	[1]
Ending balance	$ (1,917)	[1]	$ (2,661)	[1]	$ (1,917)	[1]	$ (2,661)	[1]	$ 28	[1]	$ 199	[1]	$ 0	[1]	$ (1)	[1]	$ (1,929)	[1]	$ (2,907)	[1]	$ (16)	[1]	$ (5)	[1]	$ 0	[1]	$ 53	[1]	$ 11	[1]	$ 243	[1]	$ 11	[1]	$ 243	[1]	$ 28	[1]	$ 196	[1]	$ (1)	[1]	$ (1)	[1]	$ 0	[1]	$ 0	[1]	$ (16)	[1]	$ (5)	[1]	$ 0	[1]	$ 53	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]	$ 1	[1]

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

[2] See tables following changes in accumulated other comprehensive income tables for details about these reclassifications.