Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions		3 Months Ended						6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2016		Mar. 23, 2016		Jun. 30, 2017		Jun. 30, 2016
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance								$ 27,612
Amounts reclassified from AOCI(b)	[1]	$ 34	$ 34					74		$ 72
Other comprehensive income		35	31					25		59
Ending balance		29,290						29,290
Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI(b)	[1]	0	0					4		3
Other comprehensive income		1	0					12		(2)
PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI(b)	[1]					$ 1
Gains and (losses) on Cash Flow Hedges
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance						(19)	[2]	(17)		(19)	[2]
OCI before reclassifications								1		(10)	[2]
Amounts reclassified from AOCI(b)								4		3	[2],[3]
Other comprehensive income	[2]							5		(7)
Ending balance	[2]	(12)	(26)	$ (26)				(12)		(26)
Gains and (losses) on Cash Flow Hedges | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance						(21)	[2]	(19)		(21)	[2]
OCI before reclassifications								1		(7)	[2]
Amounts reclassified from AOCI(b)								4		3	[2],[3]
Other comprehensive income	[2]							5		(4)
Ending balance	[2]	(14)	(25)	(25)				(14)		(25)
Gains and (losses) on Cash Flow Hedges | PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					0		0		0
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	0	0	0				0		0
Gains and (losses) on Cash Flow Hedges | PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			(8)	[4]	(8)				(8)
OCI before reclassifications	[2]					0
Amounts reclassified from AOCI(b)	[2],[3]					0
Other comprehensive income	[2]					0
Ending balance	[2],[4]					(8)
Unrealized Gains and (losses) on Marketable Securities
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					3		4		3
OCI before reclassifications	[2]							2		0
Amounts reclassified from AOCI(b)	[2]							0		0	[3]
Other comprehensive income	[2]							2		0
Ending balance	[2]	6	3	3				6		3
Unrealized Gains and (losses) on Marketable Securities | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					1		2		1
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	2	1	1				2		1
Unrealized Gains and (losses) on Marketable Securities | PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					1		1		1
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	1	1	1				1		1
Unrealized Gains and (losses) on Marketable Securities | PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			0	[4]	0				0
OCI before reclassifications	[2]					0
Amounts reclassified from AOCI(b)	[2],[3]					0
Other comprehensive income	[2]					0
Ending balance	[2],[4]					0
Pension and Non-Pension Postretirement Benefit Plan Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(2,565)		(2,610)		(2,565)
OCI before reclassifications	[2]							(58)		(2)
Amounts reclassified from AOCI(b)	[1]	34	34					70	[2],[3]	69	[2],[3]
Other comprehensive income	[2]							12		67
Ending balance	[2]	(2,598)	(2,498)	(2,498)				(2,598)		(2,498)
Pension and Non-Pension Postretirement Benefit Plan Items | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					0		0		0
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[1]	0	0					0	[2],[3]	0	[2],[3]
Other comprehensive income	[2]							0		0
Ending balance	[2]	0	0	0				0		0
Pension and Non-Pension Postretirement Benefit Plan Items | PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					0		0		0
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	0	0	0				0		0
Pension and Non-Pension Postretirement Benefit Plan Items | PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			(27)	[4]	(28)				(28)
OCI before reclassifications	[2]					0
Amounts reclassified from AOCI(b)	[1],[2],[3]					1
Other comprehensive income	[2]					1
Ending balance	[2],[4]					(27)
Foreign Currency Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(40)		(30)		(40)
OCI before reclassifications	[2]							3		6
Amounts reclassified from AOCI(b)	[2]							0		0	[3]
Other comprehensive income	[2]							3		6
Ending balance	[2]	(27)	(34)	(34)				(27)		(34)
Foreign Currency Items | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(40)		(30)		(40)
OCI before reclassifications	[2]							3		6
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							3		6
Ending balance	[2]	(27)	(34)	(34)				(27)		(34)
Foreign Currency Items | PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					0		0		0
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	0	0	0				0		0
Foreign Currency Items | PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			0	[4]	0				0
OCI before reclassifications	[2]					0
Amounts reclassified from AOCI(b)	[2],[3]					0
Other comprehensive income	[2]					0
Ending balance	[2],[4]					0
AOCI of Equity Investments
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(3)		(7)		(3)
OCI before reclassifications	[2]							5		(7)
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							5		(7)
Ending balance	[2]	(2)	(10)	(10)				(2)		(10)
AOCI of Equity Investments | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(3)		(7)		(3)
OCI before reclassifications	[2]							6		(4)
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							6		(4)
Ending balance	[2]	(1)	(7)	(7)				(1)		(7)
AOCI of Equity Investments | PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					0		0		0
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	0	0	0				0		0
AOCI of Equity Investments | PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			0	[4]	0				0
OCI before reclassifications	[2]					0
Amounts reclassified from AOCI(b)	[2],[3]					0
Other comprehensive income	[2]					0
Ending balance	[2],[4]					0
Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(2,624)		(2,660)		(2,624)
OCI before reclassifications	[2]							(47)		(13)
Amounts reclassified from AOCI(b)	[2]							74		72	[3]
Other comprehensive income	[2]							27		59
Ending balance	[2]	(2,633)	(2,565)	(2,565)				(2,633)		(2,565)
Total | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(63)		(54)		(63)
OCI before reclassifications	[2]							10		(5)
Amounts reclassified from AOCI(b)	[2],[3]							4		3
Other comprehensive income	[2]							14		(2)
Ending balance	[2]	(40)	(65)	(65)				(40)		(65)
Total | PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					1		1		1
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	$ 1	$ 1	1				$ 1		1
Total | PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			$ (35)	[4]	(36)				$ (36)
OCI before reclassifications	[2]					0
Amounts reclassified from AOCI(b)	[2],[3]					1
Other comprehensive income	[2]					1
Ending balance	[2],[4]					$ (35)

[1] Amounts in parenthesis represent a decrease in net income.

[2] All amounts are net of tax and noncontrolling interest. Amounts in parenthesis represent a decrease in AOCI.

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

[4] 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.