Derivative Financial Instruments - Summary of AOCI related to Cash Flow Hedges (Details) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2016		Sep. 30, 2015		Sep. 30, 2016		Sep. 30, 2015		Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
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)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]					(106)		(152)
Income taxes		340		115		625		805
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassifications from accumulated OCI to net income		4,535		4,564		12,243		14,278
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	(56)		(60)		(56)		(60)			(63)		(36)
OCI before reclassifications	[1]					5		(30)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]					(2)		(6)
Income taxes		173		(36)		293		371
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassifications from accumulated OCI to net income		4,533		4,562		12,234		14,270
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Derivative [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	(23)		(24)		(23)		(24)			(19)		(28)
OCI before reclassifications	[1]					(1)		(18)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]					3		(22)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(23)	[1]	(24)	[1]	(23)	[1]	(24)	[1]	$ (26)		$ (19)	(28)
OCI before reclassifications				(8)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(24)	[1]	(25)	[1]	(24)	[1]	(25)	[1]		$ (21)		(18)
OCI before reclassifications	[1]					0		(13)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]					3		(6)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(24)	[1]	(25)	[1]	(24)	[1]	(25)	[1]				$ (18)
OCI before reclassifications				(7)
Energy Related Hedges [Member] | Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(24)	[1]	(25)	[1]	(24)	[1]	(25)	[1]	$ (25)		$ (21)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Income taxes	[3]	0				0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes	[3]	0				0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Derivative [Line Items]
Income taxes	[3]			(1)		2		(13)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes				(1)	[3]	$ 2	[3]	3
Interest Expense [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		3		3				8
Interest Expense [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		$ 1		$ 3				8
Interest Expense [Member] | Operating Revenue [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion								(18)
Interest Expense [Member] | Total Cash Flow Hedges [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion								(13)
Operating Revenue [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion								(2)
Operating Revenue [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion								(2)
Operating Revenue [Member] | Total Cash Flow Hedges [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion								0
Operating Revenue [Member] | Total Cash Flow Hedges [Member] | Operating Revenue One [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion								$ 16

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