Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2016		Sep. 30, 2015		Sep. 30, 2016		Sep. 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]	$ (2,523)		$ (2,596)		$ (2,523)		$ (2,596)		$ (2,624)		$ (2,684)
OCI before reclassifications	[1]					(5)		(64)
Amounts reclassified from AOCI	[1],[2]					106		152
Net current-period OCI		36		32		96		88	[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]	(23)		(24)		(23)		(24)		(19)		(28)
OCI before reclassifications	[1]					(1)		(18)
Amounts reclassified from AOCI	[1],[2]					(3)		22
Net current-period OCI	[1]					(4)		4
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]	(2,463)		(2,539)		(2,463)		(2,539)		(2,565)		(2,640)
OCI before reclassifications						(2)	[1]	(29)
Amounts reclassified from AOCI	[1],[2]					104		130
Net current-period OCI	[1]					102		101
Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(32)	[1]	(36)	[1]	(32)	[1]	(36)	[1]	(40)	[1]	(19)
OCI before reclassifications	[1]					3		(17)
Amounts reclassified from AOCI						(5)
Net current-period OCI	[1]					8		(17)
Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	(8)		0		(8)		0		(3)		0
OCI before reclassifications	[1]					(5)		0
Amounts reclassified from AOCI	[1],[2]					0		0
Net current-period OCI	[1]					(5)		0
AOCI Attributable to Parent [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Net current-period OCI	[1]					101
Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	(56)		(60)		(56)		(60)		(63)		(36)
OCI before reclassifications	[1]					5		(30)
Amounts reclassified from AOCI	[1],[2]					2		6
Net current-period OCI		4		(13)		2		(24)	[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		(24)	[1]	(25)	[1]	(24)	[1]	(25)	[1]	(21)		(18)
OCI before reclassifications	[1]					0		(13)
Amounts reclassified from AOCI	[1],[2]					(3)		6
Net current-period OCI	[1]					(3)		(7)
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		2	[1]	1	[1]	2	[1]	1	[1]	1		1	[1]
OCI before reclassifications	[1]					1		0
Net current-period OCI	[1]					1		0
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		(32)	[1]	(36)	[1]	(32)	[1]	(36)	[1]	(40)	[1]	(19)
OCI before reclassifications	[1]					3		(17)
Net current-period OCI	[1]					8		(17)
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]	(2)		0		(2)		0		(3)		0
OCI before reclassifications	[1]					1		0
Amounts reclassified from AOCI	[1],[2]					0		0
Net current-period OCI	[1]					1		0
Exelon Generation Co L L C [Member] | AOCI Attributable to Parent [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(56)				(56)				(63)
Net current-period OCI	[1]					7
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]	(41)		(35)	[3]	(41)		(36)		(46)
OCI before reclassifications						0		0
Amounts reclassified from AOCI						1		5
Net current-period OCI						1		5
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]	(8)		(8)	[3]	(8)		(8)		(9)
OCI before reclassifications						0		0
Amounts reclassified from AOCI						0		(1)
Net current-period OCI						0		1
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 and noncontrolling interest. 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.