Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2016		Jun. 30, 2015		Jun. 30, 2016		Jun. 30, 2015		Dec. 31, 2015		Dec. 31, 2014
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	$ (2,565)		$ (2,626)		$ (2,565)		$ (2,626)		$ (2,624)		$ (2,684)
OCI before reclassifications	[1]					(7)		(48)
Amounts reclassified from AOCI	[1],[2]					66		106
Net current-period OCI		31		50		59	[1]	58	[1]
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	(26)		(19)		(26)		(19)				(28)
OCI before reclassifications	[1]							(10)
Amounts reclassified from AOCI	[1],[2]							19
Net current-period OCI	[1]					(7)		9
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		3	[1]	3	[1]	3	[1]	3	[1]	3	[1]	3
OCI before reclassifications	[1]					0		0
Net current-period OCI	[1]					0		0
Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	(2,498)		(2,582)		(2,498)		(2,582)		(2,565)		(2,640)
OCI before reclassifications						(2)	[1]	(29)
Amounts reclassified from AOCI	[1],[2]					69		87
Net current-period OCI	[1]					67		58
Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(34)	[1]	(28)	[1]	(34)	[1]	(28)	[1]	(40)	[1]	(19)
OCI before reclassifications	[1]					6		(9)
Net current-period OCI	[1]					6		(9)
Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	(10)		0		(10)		0		(3)		0
OCI before reclassifications	[1]					(7)		0
Amounts reclassified from AOCI	[1],[2]					0		0
Net current-period OCI	[1]					(7)		0
Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	(65)		(47)		(65)		(47)		(63)		(36)
OCI before reclassifications	[1]					1		(14)
Amounts reclassified from AOCI	[1],[2]					(3)		3
Net current-period OCI		0		6		(2)	[1]	(11)	[1]
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]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(25)	[1]	(21)	[1]	(25)	[1]	(21)	[1]			(18)
OCI before reclassifications	[1]							(6)
Amounts reclassified from AOCI	[1],[2]							3
Net current-period OCI	[1]					(4)		(3)
Exelon Generation Co L L C [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		1	[1]	2	[1]	1	[1]	2	[1]	1		1	[1]
OCI before reclassifications	[1]					0		1
Net current-period OCI	[1]					0		1
Exelon Generation Co L L C [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]			0				0				0
Exelon Generation Co L L C [Member] | Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(34)	[1]	(28)	[1]	(34)	[1]	(28)	[1]	(40)	[1]	(19)
OCI before reclassifications	[1]					6		(9)
Net current-period OCI	[1]					6		(9)
Exelon Generation Co L L C [Member] | Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	(7)		0		(7)		0		(3)		0
OCI before reclassifications	[1]					(4)		0
Amounts reclassified from AOCI	[1],[2]					0		0
Net current-period OCI	[1]					(4)		0
PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	1		1		1		1		1		1
Net current-period OCI	[1]							0
PECO Energy Co [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	0		0		0		0		0		0
OCI before reclassifications	[1]							0
PECO Energy Co [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		1	[1]	1	[1]	1	[1]	1	[1]	1	[1]	1
OCI before reclassifications	[1]							0
PECO Energy Co [Member] | Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]							0
PECO Energy Co [Member] | Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]							0
PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(35)	[3]	(42)		(35)	[3]	(42)		(36)		(46)
OCI before reclassifications						0		0
Amounts reclassified from AOCI						1		4
Net current-period OCI						1		4
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]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(8)	[3]	(9)		(8)	[3]	(9)		(8)		(9)
OCI before reclassifications						0		0
Amounts reclassified from AOCI						0		0
Net current-period OCI						0		0
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		0	[3]	0		0	[3]	0		0		0
OCI before reclassifications						0		0
Amounts reclassified from AOCI						0
Net current-period OCI						0		0
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(27)	[3]	(33)		(27)	[3]	(33)		(28)		(37)
OCI before reclassifications						0		0
Amounts reclassified from AOCI						1		4
Net current-period OCI						1		4
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		0	[3]	0		0	[3]	0		0		0
OCI before reclassifications						0		0
Amounts reclassified from AOCI						0		0
Net current-period OCI						0		0
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		$ 0	[3]	$ 0		0	[3]	0		$ 0		$ 0
OCI before reclassifications						0		0
Amounts reclassified from AOCI						0		0
Net current-period OCI						$ 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.

[3] As a result of the PHI Merger, the PHI predecessor balances at March 23, 2016 were reduced to zero on March 24, 2016 due to purchase accounting adjustments applied to PHI.