Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2012

Commitments And Contingencies Tables Disclosure [Line Items]

Energy Commitments [Text Block]

	Net Capacity			Power			Transmission Rights			Purchased Energy
	Purchases (a)			Purchases (b)			Purchases (c)			from CENG			Total
2012		$	391		$	61		$	26		$	677		$	1,155
2013			360			67			32			583			1,042
2014			354			34			26			351			765
2015			351			9			13			—			373
2016			265			4			2			—			271
Thereafter			668			6			36			—			710
Total		$	2,389		$	181		$	135		$	1,611		$	4,316

(a)       Net capacity purchases include PPAs and other capacity contracts including those that are accounted for as operating leases. Amounts presented in the commitments represent Generation's expected payments under these arrangements at March 31, 2012, net of fixed capacity payments expected to be received by Generation under contracts to resell such acquired capacity to third parties under long-term capacity sale contracts. Expected payments include certain capacity charges which are contingent on plant availability.

(b)       Excludes renewable energy PPA contracts that are contingent in nature.

(c)       Transmission rights purchases include estimated commitments for additional transmission rights that will be required to fulfill firm sales contracts.

Utility Energy Purchase Commitments [Text Block]

			Expiration within
													2017
	Total		2012		2013		2014		2015		2016		and beyond
ComEd
Electric supply procurement (a)	$	1,182	$	95	$	367	$	309	$	134	$	137	$	140
Renewable energy and RECs (b)		1,697		36		71		74		74		81		1,361
PECO
Electric supply procurement (c)		1,208		675		416		93		24		-		-
AECs		39		7		11		9		2		2		8
Curtailment services		12		12		-		-		-		-		-
BGE
Electric supply procurement (d)		1,299		646		544		109		-		-		-
Curtailment services		144		31		49		46		18		-		-

(a)       ComEd entered into various contracts for the procurement of electricity that expire between 2012 and 2017. ComEd is permitted to recover its electric supply procurement costs from retail customers with no mark-up. See Note 4- Regulatory Matters for additional information.

(b)       ComEd entered into various contracts for the procurement of renewable energy and RECs that expire between 2012 and 2032. ComEd is permitted to recover its renewable energy and REC costs from retail customers with no mark-up. See Note 4 - Regulatory Matters for additional information.

(c)       PECO entered into various contracts for the procurement of electric supply to serve its default service customers that expire between 2012 and 2015. PECO is permitted to recover its electric supply procurement costs from default service customers with no mark-up in accordance with its PAPUC-approved DSP Program. See Note 4 - Regulatory Matters for additional information.

(d)       BGE entered into various contracts for the procurement of electricity that expire between 2012 and 2014. The cost of power under these contracts is recoverable under MDPSC approved fuel clauses.See Note 4 - Regulatory Matters for additional information.

Fuel Purchase Commitments [Text Block]

			Expiration within
													2017
	Total		2012		2013		2014		2015		2016		and beyond
Generation	$	8,343	$	975	$	1,076	$	1,097	$	1,129	$	732	$	3,334
PECO		494		137		97		78		55		34		93
BGE		656		85		84		70		52		51		314

			Expiration within
													2017
	Total		2012		2013		2014		2015		2016		and beyond
Exelon	$	1,043	$	525	$	167	$	127	$	87	$	25	$	112
Generation		597		308		99		90		67		5		28
ComEd		90		85		5		—		—		—		—
PECO		105		60		18		17		1		1		8
BGE		18		7		11		—		—		—		—

Commercial Commitments [Text Block]

		Exelon			Generation			ComEd			PECO			BGE
Letters of credit (non-debt)(a)	$	2,623		$	1,381		$	23		$	21		$	1
Guarantees		10,696	(b)		1,448	(c)		209	(d)		181	(e)		253	(f)
Nuclear insurance premiums		2,098			2,098			0			0			0
Total commercial commitments	$	15,417		$	4,927		$	232		$	202		$	254

Accrued environmental liabilities [Text Block]

March 31, 2012	Total Environmental Investigation and Remediation Reserve		Portion of Total Related to MGP Investigation and Remediation
Exelon	$	223	$	163
Generation		51		0
ComEd		123		116
PECO		49		46
December 31, 2011	Total Environmental Investigation and Remediation Reserve		Portion of Total Related to MGP Investigation and Remediation
Exelon	$	224	$	168
Generation		47		0
ComEd		127		121
PECO		50		47