Derivative Financial Instruments - Summary of AOCI related to Cash Flow Hedges (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Accumulated other comprehensive loss, net		$ (2,660)	$ (2,624)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	(150)	(196)	[2],[3]
Other, net [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax			10
Interest Expense [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax		5	4
Exelon Generation Co L L C [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Accumulated other comprehensive loss, net		(54)	(63)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	(13)	(5)	[2],[3]
Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Accumulated other comprehensive loss, net		(17)	(19)		$ (28)
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		(6)	(12)
Cash Flow Hedging [Member] | Other, net [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			16
Cash Flow Hedging [Member] | Interest Expense [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		8	7
Cash Flow Hedging [Member] | Operating Revenue [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(2)
Cash Flow Hedging [Member] | Exelon Generation Co L L C [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Accumulated other comprehensive loss, net		(19)	(21)		$ (18)
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		(6)	(8)
Cash Flow Hedging [Member] | Exelon Generation Co L L C [Member] | Other, net [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			0
Cash Flow Hedging [Member] | Exelon Generation Co L L C [Member] | Interest Expense [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		$ 8	7
Cash Flow Hedging [Member] | Exelon Generation Co L L C [Member] | Operating Revenue [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			$ (2)

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

[2] All amounts are net of tax and noncontrolling interests. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.

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