Income Taxes (Details) (USD $)	0 Months Ended	3 Months Ended				12 Months Ended
	Jan. 13, 2011	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Effective Income Tax Rate Reconciliation
U.S. Federal statutory rate						35.00%	[1]	35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit						4.70%	[1]	(3.60%)	4.40%
Qualified nuclear decommissioning trust fund income (losses)						3.70%	[1]	5.40%	0.50%
Domestic production activities deduction									(0.30%)
Tax exempt income						(0.20%)	[1]	(0.20%)	(0.20%)
Nontaxable postretirement benefits								(1.10%)
Health Care Reform Legislation						0.10%	[1]	0.10%	(0.20%)
Amortization of investment tax credit						(1.90%)	[1]	2.20%	(0.30%)
Plant basis differences						(1.60%)	[1]	(2.40%)	(1.00%)
Production Tax Credits						(2.10%)	[1]		0.90%
Fines and Penalties								(2.60%)
Merger Expenses								(2.40%)
Other						(0.10%)	[1]	(1.10%)	(0.20%)
Effective income tax rate						37.60%	[1]	34.90%	36.80%
Unrecognized Tax Benefits For Which Timing Of Ultimate Benefits Uncertain [Abstract]
Tax positions for which there is uncertainty about the timing of tax benefits		$ 730,000,000				$ 1,387,000,000		$ 730,000,000
Accounting for Uncertainty in Income Taxes [Abstract]
Unrecognized tax benefits that if recognized would affect the effective tax rate		294,000,000				788,000,000		294,000,000
Increases based on tax positions prior to current year						(493,000,000)		(91,000,000)	3,000,000
Interest recognized related to uncertain tax positions [Abstract]
Net interest receivable (payable) recognized related to uncertain tax positions		31,000,000				(349,000,000)		31,000,000
Net interest (income) expense recognized related to uncertain tax positions						391,000,000		(1,000,000)	(56,000,000)
1999 Sale of Fossil Generating Assets [Abstract]
Deferred tax gain on sale of fossil generating assets						2,800,000,000
Deferred tax gain under involuntary conversion provisions of the IRC						1,600,000,000
Deferred tax gain under like-kind exchange provisions of the IRC						1,200,000,000
IRS asserted penalties for understatement of tax						87,000,000
Potential tax and interest from a successful IRS challenge of the like-kind exchange transaction position						840,000,000
Potential interest expense from a successful IRS challenge of the like-kind exchange position						305,000,000
Unsuccessful Litigation Determinations [Abstract]
Expected non-cash charge to earnings						265,000,000
Unrecognized tax benefits for Generation Repairs						107,000,000
FIN 48 Tax Remeasurement [Abstract]
FIN 48 Tax Remeasurement Interest Expense									65,000,000
Tax Settlement [Abstract]
Payment to IRS for open tax positions									302,000,000
State Tax Legislation [Abstract]
Current Illinois state corporate tax rate	7.30%
IL State Deferred Income Tax Expense due to rate change					7,000,000
Regulatory asset related to state tax rate change					15,000,000
Additional Income Tax Expense (Benefit) Due To 2011 New Tax Law				12,000,000
Change in state income tax provision due to rate change				7,000,000
Income tax benefit recorded as a result of re-apportionment of state income taxes [Abstract]
Income tax benefit recorded as a result of re-apportionment of state income taxes		3,000,000	116,000,000	1,000,000	22,000,000
Deferred state tax liability resulting from purchase accounting			44,000,000
DeferredStateTaxAssetFromStateTaxApportionment			72,000,000
Income and cash tax benefit as a result of repair costs deduction [Abstract]
Cash tax benefit (detriment) as a result of repair costs deduction									300,000,000
Gas Distribution Repair Tax Benefit Expense								26,000,000	26,000,000
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance			807,000,000		787,000,000	1,024,000,000		807,000,000	787,000,000
Merger Balance Transfer								195,000,000
Increases based on tax positions related to current year						19,000,000		34,000,000	5,000,000
Changes to tax positions that only affect timing						649,000,000		(88,000,000)	21,000,000
Increases based on tax positions prior to current year						(493,000,000)		(91,000,000)	3,000,000
Decreases based on tax positions prior to current year						6,000,000		6,000,000
Decreases related to settlements with taxing authorities						0		2,000,000
Decreases from expiration of statute of limitations						(4,000,000)		(7,000,000)	(3,000,000)
Unrecognized tax benefits - ending balance		1,024,000,000		807,000,000		2,175,000,000		1,024,000,000	807,000,000
Income Tax Expense Benefit Continuing Operations [Line Items]
Income Tax Expense (Benefit)						1,044,000,000		627,000,000	1,457,000,000
Operating Loss Carryforwards [Line Items]
Federal net operating loss						377,000,000	[2]
Federal general business credits carryforward						556,000,000
State net operating loss carryforward						3,061,000,000	[3]
Deferred taxes						161,000,000
Valuation allowance						13,000,000
Tax Effects Of Temporary Differences [Line Items]
Plant basis differences		(10,689,000,000)				(11,612,000,000)		(10,689,000,000)
Accrual based contracts		(389,000,000)				(214,000,000)		(389,000,000)
Unrealized gains on derivative financial instruments		(392,000,000)				(509,000,000)		(392,000,000)
Deferred pension and other post-retirement obligation		2,356,000,000				1,489,000,000		2,356,000,000
Nuclear decommissioning activities		(604,000,000)				(647,000,000)		(604,000,000)
Deferred debt refinancing costs		(537,000,000)				173,000,000		(537,000,000)
Net operating losses		421,000,000				252,000,000		421,000,000
Tax credit carry-forward		226,000,000				534,000,000		226,000,000
Investment in CENG		(405,000,000)				(541,000,000)		(405,000,000)
Other, net		701,000,000				804,000,000		701,000,000
Deferred income tax liabilities, net		(11,169,000,000)				(11,882,000,000)		(11,169,000,000)
Unamortized investment tax credits		(251,000,000)				(490,000,000)		(251,000,000)
Total deferred income tax liabilities, net and unamortized investment tax credits		(11,420,000,000)				(12,372,000,000)		(11,420,000,000)
Federal Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						744,000,000		37,000,000	1,000,000
Deferred Income Tax Expense Benefit						140,000,000		701,000,000	1,200,000,000
Investment tax credit amortization						(15,000,000)		(11,000,000)	(12,000,000)
State Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						181,000,000		(25,000,000)	(3,000,000)
Deferred Income Tax Expense Benefit						(6,000,000)		(75,000,000)	271,000,000
More Than One Year And Within Four Years [Member]
State Tax Legislation [Abstract]
New Illinois state corporate tax rate as a result of 2011 Illinois State Tax Rate Legislation	9.50%
More Than Four Years And Within Fourteen Years [Member]
State Tax Legislation [Abstract]
Current Illinois state corporate tax rate	9.50%
New Illinois state corporate tax rate as a result of 2011 Illinois State Tax Rate Legislation	7.75%
More Than Fifteen Years [Member]
State Tax Legislation [Abstract]
Current Illinois state corporate tax rate	7.75%
New Illinois state corporate tax rate as a result of 2011 Illinois State Tax Rate Legislation	7.30%
Exelon Generation Co L L C [Member]
Effective Income Tax Rate Reconciliation
U.S. Federal statutory rate						35.00%	[1]	35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit						1.60%	[1]	4.70%	4.50%
Qualified nuclear decommissioning trust fund income (losses)						6.10%	[1]	9.10%	0.70%
Domestic production activities deduction									(0.40%)
Tax exempt income						(0.30%)	[1]	(0.40%)	(0.20%)
Nontaxable postretirement benefits								(1.30%)
Health Care Reform Legislation									0.00%
Amortization of investment tax credit						(3.00%)	[1]	3.70%	(0.30%)
Production Tax Credits						(3.40%)	[1]		1.20%
Uncertain Tax Position Remeasurement									0.00%
Fines and Penalties								(4.40%)
Other						0.70%	[1]	(0.50%)	(0.70%)
Effective income tax rate						36.70%	[1]	47.30%	37.40%
Accounting for Uncertainty in Income Taxes [Abstract]
Unrecognized tax benefits that if recognized would affect the effective tax rate		263,000,000				768,000,000		263,000,000
Information by nature of uncertainty related to unrecognized tax benefits						84,000,000
Increases based on tax positions prior to current year						(493,000,000)		(91,000,000)	3,000,000
Interest recognized related to uncertain tax positions [Abstract]
Net interest receivable (payable) recognized related to uncertain tax positions		(20,000,000)				(37,000,000)		(20,000,000)
Net interest (income) expense recognized related to uncertain tax positions						17,000,000		11,000,000	(40,000,000)
Status Of Like Kind Exchange Position [Abstract]
Receivable from Exelon intercompany money pool						44,000,000
FIN 48 Tax Remeasurement [Abstract]
FIN 48 Tax Remeasurement Current Tax Expense (Benefit)									(70,000,000)
State Tax Legislation [Abstract]
Current Illinois state corporate tax rate	7.30%
IL State Deferred Income Tax Expense due to rate change					11,000,000
Additional Income Tax Expense (Benefit) Due To 2011 New Tax Law				5,000,000
Income tax benefit recorded as a result of re-apportionment of state income taxes [Abstract]
Income tax benefit recorded as a result of re-apportionment of state income taxes		7,000,000	14,000,000	8,000,000	11,000,000
Deferred state tax liability resulting from purchase accounting			14,000,000
Income and cash tax benefit as a result of repair costs deduction [Abstract]
Cash tax benefit (detriment) as a result of repair costs deduction									28,000,000
Allocated tax benefits [Abstract]
Allocated tax benefits						26,000,000		48,000,000	30,000,000
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance			683,000,000		664,000,000	876,000,000		683,000,000	664,000,000
Merger Balance Transfer								183,000,000
Increases based on tax positions related to current year						19,000,000		3,000,000	1,000,000
Changes to tax positions that only affect timing						36,000,000		(69,000,000)	24,000,000
Increases based on tax positions prior to current year						(493,000,000)		(91,000,000)	3,000,000
Decreases based on tax positions prior to current year						5,000,000		6,000,000
Decreases related to settlements with taxing authorities						0		2,000,000
Decreases from expiration of statute of limitations						(4,000,000)		(7,000,000)	(3,000,000)
Unrecognized tax benefits - ending balance		876,000,000		683,000,000		1,415,000,000		876,000,000	683,000,000
Income Tax Expense Benefit Continuing Operations [Line Items]
Income Tax Expense (Benefit)						615,000,000		500,000,000	1,056,000,000
Operating Loss Carryforwards [Line Items]
Federal net operating loss						36,000,000
Federal general business credits carryforward						556,000,000
State net operating loss carryforward						1,498,000,000	[4]
Deferred taxes						82,000,000
Valuation allowance						11,000,000
Tax Effects Of Temporary Differences [Line Items]
Plant basis differences		(3,545,000,000)				(3,879,000,000)		(3,545,000,000)
Accrual based contracts		(389,000,000)				(214,000,000)		(389,000,000)
Unrealized gains on derivative financial instruments		(479,000,000)				(505,000,000)		(479,000,000)
Deferred pension and other post-retirement obligation		(439,000,000)				(362,000,000)		(439,000,000)
Nuclear decommissioning activities		(604,000,000)				(646,000,000)		(604,000,000)
Deferred debt refinancing costs		163,000,000				79,000,000		163,000,000
Net operating losses		226,000,000				76,000,000		226,000,000
Tax credit carry-forward		226,000,000				534,000,000		226,000,000
Investment in CENG		(419,000,000)				(541,000,000)		(419,000,000)
Other, net		9,000,000				67,000,000		9,000,000
Deferred income tax liabilities, net		(5,251,000,000)				(5,391,000,000)		(5,251,000,000)
Unamortized investment tax credits		(216,000,000)				(454,000,000)		(216,000,000)
Total deferred income tax liabilities, net and unamortized investment tax credits		(5,467,000,000)				(5,845,000,000)		(5,467,000,000)
Exelon Generation Co L L C [Member] | Federal Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						250,000,000		104,000,000	431,000,000
Deferred Income Tax Expense Benefit						360,000,000		326,000,000	435,000,000
Investment tax credit amortization						(11,000,000)		(6,000,000)	(7,000,000)
Exelon Generation Co L L C [Member] | State Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						50,000,000		(12,000,000)	74,000,000
Deferred Income Tax Expense Benefit						(34,000,000)		88,000,000	123,000,000
Exelon Generation Co L L C [Member] | Settlement With Taxing Authority [Member]
Accounting for Uncertainty in Income Taxes [Abstract]
Information by nature of uncertainty related to unrecognized tax benefits						55,000,000
Exelon Generation Co L L C [Member] | More Than One Year And Within Four Years [Member]
State Tax Legislation [Abstract]
New Illinois state corporate tax rate as a result of 2011 Illinois State Tax Rate Legislation	9.50%
Exelon Generation Co L L C [Member] | More Than Four Years And Within Fourteen Years [Member]
State Tax Legislation [Abstract]
Current Illinois state corporate tax rate	9.50%
New Illinois state corporate tax rate as a result of 2011 Illinois State Tax Rate Legislation	7.75%
Exelon Generation Co L L C [Member] | More Than Fifteen Years [Member]
State Tax Legislation [Abstract]
Current Illinois state corporate tax rate	7.75%
New Illinois state corporate tax rate as a result of 2011 Illinois State Tax Rate Legislation	7.30%
Commonwealth Edison Co [Member]
Effective Income Tax Rate Reconciliation
U.S. Federal statutory rate						35.00%		35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit						3.40%		4.60%	3.60%
Nontaxable postretirement benefits								(0.40%)
Health Care Reform Legislation						0.70%		0.40%	(1.00%)
Amortization of investment tax credit						(0.60%)			(0.40%)
Plant basis differences						(0.80%)		(0.30%)
Production Tax Credits						(0.10%)
Uncertain Tax Position Remeasurement									(0.30%)
Other						0.30%		(0.60%)	0.60%
Effective income tax rate						37.90%		38.70%	37.50%
Interest recognized related to uncertain tax positions [Abstract]
Net interest receivable (payable) recognized related to uncertain tax positions		107,000,000				(174,000,000)		107,000,000
Net interest (income) expense recognized related to uncertain tax positions						281,000,000		(20,000,000)	(14,000,000)
Unsuccessful Litigation Determinations [Abstract]
Expected non-cash charge to earnings						170,000,000
FIN 48 Tax Remeasurement [Abstract]
FIN 48 Tax Remeasurement Interest Expense									36,000,000
FIN 48 Tax Remeasurement Current Tax Expense (Benefit)									70,000,000
State Tax Legislation [Abstract]
Current Illinois state corporate tax rate	7.30%
IL State Deferred Income Tax Expense due to rate change					4,000,000
Regulatory asset related to state tax rate change					15,000,000
Additional Income Tax Expense (Benefit) Due To 2011 New Tax Law				10,000,000
Income and cash tax benefit as a result of repair costs deduction [Abstract]
Cash tax benefit (detriment) as a result of repair costs deduction									250,000,000
Allocated tax benefits [Abstract]
Allocated tax benefits									0
Non-cash contribution to equity								11,000,000
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance			70,000,000		72,000,000	67,000,000		70,000,000	72,000,000
Changes to tax positions that only affect timing						257,000,000		(3,000,000)	(2,000,000)
Unrecognized tax benefits - ending balance		67,000,000		70,000,000		324,000,000		67,000,000	70,000,000
Income Tax Expense Benefit Continuing Operations [Line Items]
Income Tax Expense (Benefit)						152,000,000		239,000,000	250,000,000
Operating Loss Carryforwards [Line Items]
Federal net operating loss						139,000,000
Tax Effects Of Temporary Differences [Line Items]
Plant basis differences		(3,537,000,000)				(3,523,000,000)		(3,537,000,000)
Unrealized gains on derivative financial instruments		(4,000,000)				(4,000,000)		(4,000,000)
Deferred pension and other post-retirement obligation		(598,000,000)				(522,000,000)		(598,000,000)
Deferred debt refinancing costs		(25,000,000)				(21,000,000)		(25,000,000)
Net operating losses		32,000,000				47,000,000		32,000,000
Other, net		83,000,000				154,000,000		83,000,000
Deferred income tax liabilities, net		(4,165,000,000)				(4,110,000,000)		(4,165,000,000)
Unamortized investment tax credits		(24,000,000)				(22,000,000)		(24,000,000)
Total deferred income tax liabilities, net and unamortized investment tax credits		(4,189,000,000)				(4,132,000,000)		(4,189,000,000)
Commonwealth Edison Co [Member] | Federal Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						160,000,000		(40,000,000)	(329,000,000)
Deferred Income Tax Expense Benefit						(27,000,000)		237,000,000	544,000,000
Investment tax credit amortization						(2,000,000)		(2,000,000)	(3,000,000)
Commonwealth Edison Co [Member] | State Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						50,000,000		6,000,000	(123,000,000)
Deferred Income Tax Expense Benefit						(29,000,000)		38,000,000	161,000,000
Commonwealth Edison Co [Member] | More Than One Year And Within Four Years [Member]
State Tax Legislation [Abstract]
New Illinois state corporate tax rate as a result of 2011 Illinois State Tax Rate Legislation	9.50%
Commonwealth Edison Co [Member] | More Than Four Years And Within Fourteen Years [Member]
State Tax Legislation [Abstract]
Current Illinois state corporate tax rate	9.50%
New Illinois state corporate tax rate as a result of 2011 Illinois State Tax Rate Legislation	7.75%
Commonwealth Edison Co [Member] | More Than Fifteen Years [Member]
State Tax Legislation [Abstract]
Current Illinois state corporate tax rate	7.75%
New Illinois state corporate tax rate as a result of 2011 Illinois State Tax Rate Legislation	7.30%
PECO Energy Co [Member]
Effective Income Tax Rate Reconciliation
U.S. Federal statutory rate						35.00%		35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit						1.60%		2.00%	(0.50%)
Nontaxable postretirement benefits								(0.30%)
Health Care Reform Legislation									0.00%
Amortization of investment tax credit						(0.10%)			(0.30%)
Plant basis differences						(7.10%)		(11.50%)	(6.90%)
Production Tax Credits						0.00%
Other						(0.30%)			0.00%
Effective income tax rate						29.10%		25.00%	27.30%
Interest recognized related to uncertain tax positions [Abstract]
Net interest receivable (payable) recognized related to uncertain tax positions		2,000,000				3,000,000		2,000,000
Net interest (income) expense recognized related to uncertain tax positions						(1,000,000)		(1,000,000)	(1,000,000)
Status Of Like Kind Exchange Position [Abstract]
Receivable from Exelon intercompany money pool		0				0		0
FIN 48 Tax Remeasurement [Abstract]
FIN 48 Tax Remeasurement Interest Expense									22,000,000
Income and cash tax benefit as a result of repair costs deduction [Abstract]
Cash tax benefit (detriment) as a result of repair costs deduction									95,000,000
Gas Distribution Repair Tax Benefit Expense								29,000,000	29,000,000
Allocated tax benefits [Abstract]
Allocated tax benefits						27,000,000		9,000,000	18,000,000
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance			48,000,000		44,000,000	44,000,000		48,000,000	44,000,000
Increases based on tax positions related to current year								0	4,000,000
Changes to tax positions that only affect timing						0			0
Unrecognized tax benefits - ending balance		44,000,000		48,000,000		44,000,000		44,000,000	48,000,000
Income Tax Expense Benefit Continuing Operations [Line Items]
Income Tax Expense (Benefit)						162,000,000		127,000,000	146,000,000
Operating Loss Carryforwards [Line Items]
State net operating loss carryforward						167,000,000	[5]
Deferred taxes						11,000,000
Tax Effects Of Temporary Differences [Line Items]
Plant basis differences		(2,437,000,000)				(2,573,000,000)		(2,437,000,000)
Deferred pension and other post-retirement obligation		(11,000,000)				0		(11,000,000)
Deferred debt refinancing costs		(4,000,000)				(3,000,000)		(4,000,000)
Net operating losses		14,000,000				11,000,000		14,000,000
Other, net		100,000,000				122,000,000		100,000,000
Deferred income tax liabilities, net		(2,288,000,000)				(2,401,000,000)		(2,288,000,000)
Unamortized investment tax credits		(3,000,000)				(3,000,000)		(3,000,000)
Total deferred income tax liabilities, net and unamortized investment tax credits		(2,291,000,000)				(2,404,000,000)		(2,291,000,000)
PECO Energy Co [Member] | Federal Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						126,000,000		88,000,000	(71,000,000)
Deferred Income Tax Expense Benefit						23,000,000		25,000,000	223,000,000
Investment tax credit amortization						(1,000,000)		(2,000,000)	(2,000,000)
PECO Energy Co [Member] | State Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						16,000,000		4,000,000	(37,000,000)
Deferred Income Tax Expense Benefit						(2,000,000)		12,000,000	33,000,000
Baltimore Gas and Electric Company [Member]
Effective Income Tax Rate Reconciliation
U.S. Federal statutory rate						35.00%	[6]	35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit						4.90%	[6]	24.30%	5.20%
Health Care Reform Legislation						0.20%	[6]	11.60%	(0.50%)
Amortization of investment tax credit						0.00%	[6]	(8.60%)	(0.50%)
Plant basis differences						(0.20%)	[6]	(9.00%)	(2.00%)
Production Tax Credits						0.00%
Merger Expenses								(24.20%)
Other						(0.90%)	[6]	(13.90%)	(1.70%)
Effective income tax rate						39.00%	[6]	63.60%	35.50%
Interest recognized related to uncertain tax positions [Abstract]
Net interest receivable (payable) recognized related to uncertain tax positions		0						0
Net interest (income) expense recognized related to uncertain tax positions								9,000,000	(3,000,000)
Income and cash tax benefit as a result of repair costs deduction [Abstract]
Cash tax benefit (detriment) as a result of repair costs deduction									27,000,000
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance			11,000,000		73,000,000	0		11,000,000	73,000,000
Changes to tax positions that only affect timing						0		(11,000,000)	(62,000,000)
Unrecognized tax benefits - ending balance		0		11,000,000		0		0	11,000,000
Income Tax Expense Benefit Continuing Operations [Line Items]
Income Tax Expense (Benefit)						134,000,000		7,000,000	75,000,000
Operating Loss Carryforwards [Line Items]
Federal net operating loss						31,000,000
State net operating loss carryforward						768,000,000	[7]
Deferred taxes						41,000,000
Valuation allowance						1,000,000
Tax Effects Of Temporary Differences [Line Items]
Plant basis differences		(1,553,000,000)				(1,538,000,000)		(1,553,000,000)
Deferred pension and other post-retirement obligation		(12,000,000)				(74,000,000)		(12,000,000)
Deferred debt refinancing costs		(4,000,000)				(5,000,000)		(4,000,000)
Net operating losses						52,000,000
Other, net		67,000,000				26,000,000		67,000,000
Deferred income tax liabilities, net		(1,650,000,000)				(1,792,000,000)		(1,650,000,000)
Unamortized investment tax credits		(6,000,000)				(6,000,000)		(6,000,000)
Total deferred income tax liabilities, net and unamortized investment tax credits		(1,656,000,000)				(1,798,000,000)		(1,656,000,000)
Baltimore Gas and Electric Company [Member] | Federal Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						9,000,000		(97,000,000)	(71,000,000)
Deferred Income Tax Expense Benefit						100,000,000		101,000,000	130,000,000
Investment tax credit amortization						(1,000,000)		(1,000,000)	(1,000,000)
Baltimore Gas and Electric Company [Member] | State Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit									0
Deferred Income Tax Expense Benefit						26,000,000		4,000,000	17,000,000
Exelon Corporate [Member]
Tax Effects Of Temporary Differences [Line Items]
Net operating losses		$ 105,000,000						$ 105,000,000

[1] Exelon activity for the twelve months ended December 31, 2012 includes the results of Constellation and BGE for March 12, 2012 - December 31, 2012. Generation activity for the twelve months ended December 31, 2012 includes the results of Constellation for March 12, 2012 - December 31, 2012.

[2] Exelon's federal net operating loss will expire beginning in 2031

[3] Exelon’s state net operating losses and other carryforwards, which are presented on a post-apportioned basis, will expire beginning in 2014

[4] Generation’s state net operating losses losses and other carryforwards, which are presented on a post-apportioned basis, will expire beginning in 2014

[5] PECO’s state net operating losses will expire beginning in 203

[6] BGE activity represents the activity for the twelve months ended December 31, 2012 and 2011.

[7] BGE’s state net operating losses will expire beginning in 202