Derivative Financial Instruments (Interest Rate Risk) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Cost Of Capital Strategies [Abstract]
Hypothetical increase in interest rates associated with variable-rate debt	50.00%
Pre-tax net income impact associated with a hypothetical 10% increase in interest rates - exclusive upper bound	$ 5,000,000
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (current assets)			4,000,000
Mark-to-market derivative assets (noncurrent assets)			59,000,000
Total mark-to-market derivative assets			63,000,000
Mark-to-market derivative liabilities (current liabilities)			(2,000,000)
Mark-to-market derivative liabilities (noncurrent liabilities)			(31,000,000)
Total mark-to-market derivative liabilities			(33,000,000)
Total mark-to-market derivative net assets (liabilities)			30,000,000
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Gain on swaps/borrowings	11,000,000
Loss on swaps/borrowings			(3,000,000)		(1,000,000)
Interest Rate Risk - Fair Value Hedges [Abstract]
Fair value of interest rate swaps from merger acquiree	150,000,000
Interest Rate Risk - Cash Flow Hedges [Abstract]
Mark-to-market derivative liabilities	300,000,000		281,000,000
Unrealized Gain (Loss) on Derivatives	445,000,000		604,000,000		(291,000,000)
Derivative, Notional Amount	2,651,000,000		2,498,000,000
Designated as Hedging Instrument [Member]
Interest Rate Risk - Cash Flow Hedges [Abstract]
Notional Amount of Pre-issuance Interest Rate Cash Flow Hedge Derivatives	190,000,000
Notional amounts on forward starting interest rate swaps	1,000,000
Designated as Hedging Instrument [Member] | Interest Rate Cash Flow Hedge Derivatives | Cash Flow Hedging [Member]
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative liabilities (noncurrent liabilities)	(1,000,000)
Interest Rate Risk - Cash Flow Hedges [Abstract]
Deferred Gain on Derivatives	26,000,000
Designated as Hedging Instrument [Member] | Interest Rate Swap | Fair Value Hedging [Member]
Interest Rate Risk - Cash Flow Hedges [Abstract]
Unrealized Gain (Loss) on Derivatives	26,000,000		49,000,000
Derivative, Notional Amount	1,275,000,000		650,000,000
Designated as Hedging Instrument [Member] | Interest Expense [Member] | Fair Value Hedging [Member]
Interest Rate Risk - Cash Flow Hedges [Abstract]
Increase In Notional Amount Of Derivative Instruments	625,000,000
Designated as Hedging Instrument [Member] | Interest Expense [Member] | Interest Rate Swap | Fair Value Hedging [Member]
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Loss on swaps/borrowings	(24,000,000)		(9,000,000)
Derivative [Member] | Interest Rate Swap
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (current assets)	(1,000,000)
Mark-to-market derivative assets (noncurrent assets)	38,000,000
Total mark-to-market derivative assets	37,000,000
Mark-to-market derivative liabilities (current liabilities)	(1,000,000)
Mark-to-market derivative liabilities (noncurrent liabilities)	(15,000,000)
Total mark-to-market derivative liabilities	(16,000,000)
Total mark-to-market derivative net assets (liabilities)	21,000,000
Interest Rate Risk - Cash Flow Hedges [Abstract]
Derivative, Notional Amount	1,425,000,000
Derivative [Member] | Interest Expense [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap | Fair Value Hedging [Member]
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Gain on swaps/borrowings					1,000,000
Exelon Generation Co L L C [Member]
Cost Of Capital Strategies [Abstract]
Pre-tax net income impact associated with a hypothetical 10% increase in interest rates - exclusive upper bound	5,000,000
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (current assets)			4,000,000
Mark-to-market derivative assets (noncurrent assets)			46,000,000
Total mark-to-market derivative assets			50,000,000
Mark-to-market derivative liabilities (current liabilities)			(2,000,000)
Mark-to-market derivative liabilities (noncurrent liabilities)			(31,000,000)
Total mark-to-market derivative liabilities			(33,000,000)
Total mark-to-market derivative net assets (liabilities)			17,000,000
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Loss on swaps/borrowings			(6,000,000)	[1]
Interest Rate Risk - Cash Flow Hedges [Abstract]
DOE loan guarantee	646,000,000
DOE interest rate swap	485,000,000
Mark-to-market derivative liabilities	120,000,000		232,000,000
Unrealized Gain (Loss) on Derivatives	448,000,000		611,000,000		(291,000,000)
Exelon Generation Co L L C [Member] | Interest Rate Swap
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (current assets)	(1,000,000)
Mark-to-market derivative assets (noncurrent assets)	31,000,000
Total mark-to-market derivative assets	30,000,000
Mark-to-market derivative liabilities (current liabilities)	(1,000,000)
Mark-to-market derivative liabilities (noncurrent liabilities)	(11,000,000)
Total mark-to-market derivative liabilities	(12,000,000)
Total mark-to-market derivative net assets (liabilities)	18,000,000
Exelon Generation Co L L C [Member] | Antelope Valle [Member]
Interest Rate Risk - Cash Flow Hedges [Abstract]
Percentage of interest rate swap in relation to DOE guarantee	75
Notional amount of interest rate swap DOE advance	350,000,000
Percent of DOE loan advance offset	75.00%
Notional amount of remaining cash flow hedges	135,000,000
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member]
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (noncurrent assets)			38,000,000
Total mark-to-market derivative assets			38,000,000
Mark-to-market derivative liabilities (current liabilities)			(1,000,000)
Mark-to-market derivative liabilities (noncurrent liabilities)			(31,000,000)
Total mark-to-market derivative liabilities			(32,000,000)
Total mark-to-market derivative net assets (liabilities)			6,000,000
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Interest Rate Cash Flow Hedge Derivatives | Cash Flow Hedging [Member]
Interest Rate Risk - Fair Value Hedges [Abstract]
Notional amount of interest rate swaps acquired from merger	28,000,000
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Foreign Currency Fair Value Hedge Derivatives
Interest Rate Risk - Cash Flow Hedges [Abstract]
Derivative, Notional Amount	195,000,000
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (noncurrent assets)	26,000,000
Total mark-to-market derivative assets	26,000,000
Mark-to-market derivative liabilities (current liabilities)	(1,000,000)
Mark-to-market derivative liabilities (noncurrent liabilities)	(10,000,000)
Total mark-to-market derivative liabilities	(11,000,000)
Total mark-to-market derivative net assets (liabilities)	15,000,000
Interest Rate Risk - Cash Flow Hedges [Abstract]
Derivative, Notional Amount	144,000,000
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap | Fair Value Hedging [Member]
Interest Rate Risk - Fair Value Hedges [Abstract]
Interest rate swaps previously held by acquiree	550,000,000		550,000,000
Interest Rate Risk - Cash Flow Hedges [Abstract]
Unrealized Gain (Loss) on Derivatives	23,000,000		38,000,000
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap | Cash Flow Hedging [Member]
Interest Rate Risk - Cash Flow Hedges [Abstract]
Derivative, Notional Amount	470,000,000
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Other Solar Projects [Member]
Interest Rate Risk - Cash Flow Hedges [Abstract]
Notional amounts on forward starting interest rate swaps	27,000,000
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Other Solar Projects [Member] | Interest Rate Cash Flow Hedge Derivatives | Cash Flow Hedging [Member]
Interest Rate Risk - Fair Value Hedges [Abstract]
Fair value assets	2,000,000
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Interest Expense [Member] | Interest Rate Swap | Fair Value Hedging [Member]
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Loss on swaps/borrowings	(15,000,000)	[1]	(6,000,000)	[1]
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Interest Expense [Member] | Antelope Valle [Member] | Interest Rate Cash Flow Hedge Derivatives | Cash Flow Hedging [Member]
Interest Rate Risk - Cash Flow Hedges [Abstract]
Derivative, Notional Amount	485,000,000
Exelon Generation Co L L C [Member] | Derivative [Member]
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (current assets)			3,000,000
Mark-to-market derivative assets (noncurrent assets)			8,000,000
Total mark-to-market derivative assets			11,000,000
Mark-to-market derivative liabilities (current liabilities)			(1,000,000)
Total mark-to-market derivative liabilities			(1,000,000)
Total mark-to-market derivative net assets (liabilities)			10,000,000
Exelon Generation Co L L C [Member] | Derivative [Member] | Interest Rate Swap
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (current assets)	3,000,000
Mark-to-market derivative assets (noncurrent assets)	3,000,000
Total mark-to-market derivative assets	6,000,000
Mark-to-market derivative liabilities (current liabilities)	(1,000,000)
Mark-to-market derivative liabilities (noncurrent liabilities)	(1,000,000)
Total mark-to-market derivative liabilities	(2,000,000)
Total mark-to-market derivative net assets (liabilities)	4,000,000
Exelon Generation Co L L C [Member] | Derivative [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Swap
Interest Rate Risk - Cash Flow Hedges [Abstract]
Unrealized Gain (Loss) on Derivatives	2,000,000
Exelon Generation Co L L C [Member] | Derivative [Member] | Antelope Valle [Member] | Interest Rate Swap
Interest Rate Risk - Cash Flow Hedges [Abstract]
Mark-to-market derivative liabilities	10,000,000
Exelon Generation Co L L C [Member] | Proprietary Trading [Member]
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (current assets)			20,000,000	[2]
Mark-to-market derivative assets (noncurrent assets)			32,000,000	[2]
Total mark-to-market derivative assets			52,000,000	[2]
Mark-to-market derivative liabilities (current liabilities)			(19,000,000)	[2]
Mark-to-market derivative liabilities (noncurrent liabilities)			(32,000,000)	[2]
Total mark-to-market derivative liabilities			(51,000,000)	[2]
Total mark-to-market derivative net assets (liabilities)			1,000,000	[2]
Exelon Generation Co L L C [Member] | Proprietary Trading [Member] | Interest Rate Swap
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (current assets)	15,000,000	[3]
Mark-to-market derivative assets (noncurrent assets)	15,000,000	[3]
Total mark-to-market derivative assets	30,000,000	[3]
Mark-to-market derivative liabilities (current liabilities)	(18,000,000)	[3]
Mark-to-market derivative liabilities (noncurrent liabilities)	(13,000,000)	[3]
Total mark-to-market derivative liabilities	(31,000,000)	[3]
Total mark-to-market derivative net assets (liabilities)	(1,000,000)	[3]
Exelon Generation Co L L C [Member] | Collateral And Netting [Member]
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (current assets)			(19,000,000)	[4]
Mark-to-market derivative assets (noncurrent assets)			(32,000,000)	[4]
Total mark-to-market derivative assets			(51,000,000)	[4]
Mark-to-market derivative liabilities (current liabilities)			19,000,000	[4]
Mark-to-market derivative liabilities (noncurrent liabilities)			32,000,000	[4]
Total mark-to-market derivative liabilities			51,000,000	[4]
Exelon Generation Co L L C [Member] | Collateral And Netting [Member] | Interest Rate Swap
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (current assets)	(19,000,000)	[5]
Mark-to-market derivative assets (noncurrent assets)	(13,000,000)	[5]
Total mark-to-market derivative assets	(32,000,000)	[5]
Mark-to-market derivative liabilities (current liabilities)	19,000,000	[5]
Mark-to-market derivative liabilities (noncurrent liabilities)	13,000,000	[5]
Total mark-to-market derivative liabilities	32,000,000	[5]
Other Segments [Member] | Designated as Hedging Instrument [Member]
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (noncurrent assets)			13,000,000
Total mark-to-market derivative assets			13,000,000
Total mark-to-market derivative net assets (liabilities)			13,000,000
Other Segments [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap
Derivative Interest Rate Risk [Abstract]
Mark-to-market derivative assets (noncurrent assets)	7,000,000
Total mark-to-market derivative assets	7,000,000
Mark-to-market derivative liabilities (noncurrent liabilities)	(4,000,000)
Total mark-to-market derivative liabilities	(4,000,000)
Total mark-to-market derivative net assets (liabilities)	$ 3,000,000

[1] For the years ended December 31, 2013 and 2012, the loss on Generation swaps included $16 million and $12 realized in earnings, respectively, with $2 million and an immaterial amount excluded from hedge effectiveness testing, respectively

[2] Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts between the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates.

[3] Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions.  The characterization of the interest rate derivative contracts between the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure.  Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates.

[4] Represents the netting of fair value balances with the same counterparty and any associated cash collateral.

[5] Represents the netting of fair value balances with the same counterparty and any associated cash collateral