Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]	$ (2,624)	$ (2,684)
OCI before reclassifications	[1]	59	(49)
Amounts reclassified from AOCI	[1],[2]	(31)	60
Net current-period OCI	[1]	28	11
Ending balance	[1]	(2,596)	(2,673)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]		(11)
Amounts reclassified from AOCI	[1],[2]	3	17
Net current-period OCI	[1]	(7)	6
Ending balance	[1]	(26)	(22)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]	3
OCI before reclassifications	[1]	(1)	0
Net current-period OCI	[1]	(1)	0
Ending balance	[1]	2	3
Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]	(2,565)	(2,640)
OCI before reclassifications	[1]	67
Amounts reclassified from AOCI	[1],[2]	(34)	43
Net current-period OCI	[1]	33	17
Ending balance	[1]	(2,532)	(2,623)
Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]	(40)
OCI before reclassifications	[1]	6	(12)
Net current-period OCI	[1]	6	(12)
Ending balance	[1]	(34)	(31)
Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]	(3)	0
OCI before reclassifications	[1]	(3)	0
Amounts reclassified from AOCI	[1],[2]	0	0
Net current-period OCI	[1]	(3)	0
Ending balance	[1]	(6)	0
Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]	(63)	(36)
OCI before reclassifications	[1]	(4)	(18)
Amounts reclassified from AOCI	[1],[2]	3	1
Net current-period OCI	[1]	(1)	(17)
Ending balance	[1]	(64)	(53)
Exelon Generation Co L L C [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]		(6)
Amounts reclassified from AOCI	[1],[2]	3	1
Net current-period OCI	[1]	(5)	(5)
Ending balance	[1]	(26)	(23)
Exelon Generation Co L L C [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]		1
OCI before reclassifications	[1]	0	0
Net current-period OCI	[1]	0	0
Ending balance	[1]	1	1
Exelon Generation Co L L C [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]		0
Ending balance	[1]		0
Exelon Generation Co L L C [Member] | Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]	(40)
OCI before reclassifications	[1]	6	(12)
Net current-period OCI	[1]	6	(12)
Ending balance	[1]	(34)	(31)
Exelon Generation Co L L C [Member] | Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]	(3)	0
OCI before reclassifications	[1]	(2)	0
Amounts reclassified from AOCI	[1],[2]	0	0
Net current-period OCI	[1]	(2)	0
Ending balance	[1]	(5)	0
PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]	1	1
Ending balance	[1]	1	1
PECO Energy Co [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]	0	0
Ending balance	[1]	0	0
PECO Energy Co [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]	1
Ending balance	[1]	1	1
PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance		(36)	(46)
OCI before reclassifications		2	0
Amounts reclassified from AOCI		1	(1)
Net current-period OCI		1	1
Ending balance		(35)	(45)
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance		(8)	(9)
OCI before reclassifications		0	0
Amounts reclassified from AOCI		0	0
Net current-period OCI		0	0
Ending balance		(8)	(9)
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance		0	0
OCI before reclassifications			0
Amounts reclassified from AOCI		0
Net current-period OCI		0	0
Ending balance		0	0
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance			(37)
OCI before reclassifications		2	0
Amounts reclassified from AOCI		1	(1)
Net current-period OCI		1	1
Ending balance		(27)	(36)
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance		0	0
OCI before reclassifications		0	0
Amounts reclassified from AOCI			0
Net current-period OCI		0	0
Ending balance		0	0
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance		0	0
OCI before reclassifications		0	0
Amounts reclassified from AOCI		0	0
Net current-period OCI		0	0
Ending balance		$ 0	$ 0

[1] All amounts are net of tax. Amounts in parenthesis represent a decrease in AOCI.

[2] See next tables for details about these reclassifications.