Derivative Financial Instruments - Summary of AOCI related to Cash Flow Hedges (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2016		Jun. 30, 2015		Jun. 30, 2016		Jun. 30, 2015		Mar. 31, 2016	Dec. 31, 2015		Mar. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
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)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]					(66)		(106)
Income taxes		102		327		285		690
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassifications from accumulated OCI to net income		3,234		4,080		7,708		9,714
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	(65)		(47)		(65)		(47)			(63)			(36)
OCI before reclassifications	[1]					1		(14)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]					3		(3)
Income taxes		(31)		181		120		407
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassifications from accumulated OCI to net income		3,231		4,079		7,702		9,709
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Derivative [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	(26)		(19)		(26)		(19)						(28)
OCI before reclassifications	[1]							(10)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]							(19)
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		(26)	[1]	(19)	[1]	(26)	[1]	(19)	[1]	$ (26)	(19)	[1]	$ (22)	(28)
OCI before reclassifications				1		(4)	[1]
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		(25)	[1]	(21)	[1]	(25)	[1]	(21)	[1]					(18)
OCI before reclassifications	[1]							(6)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]							(3)
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		(25)	[1]	(21)	[1]	(25)	[1]	(21)	[1]		$ (21)			$ (18)
OCI before reclassifications				0		(1)	[1]
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		(25)	[1]	(21)	[1]	(25)	[1]	(21)	[1]	$ (26)			$ (23)
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]			0		2		(10)
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				0	[3]	2	[3]	0
Interest Expense [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion				(2)
Interest Expense [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]					3
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		0		2				5
Interest Expense [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion				(2)
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]
Derivative [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]					$ 3
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		$ 1		$ 2				5
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								(10)
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								(6)
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. 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.