Fair Value of Financial Assets and Liabilities - Fair Value Measurements of Assets and Liabilities, Recurring and Nonrecurring (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	$ 1,876		$ 1,230
Fixed income
Other investments	16		15
Total assets	13,902		11,162
Deferred compensation obligation	(105)		(114)
Total liabilities	(645)		(573)
Total net assets	13,257		10,589
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	(105)		(114)
Mark-to-market derivative liabilities	291		300
Derivative Liability, Current	249		159
Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	323		459
Equity
Individually held	2,569		1,776
Exchange traded funds	170		115
Commingled funds	2,365		2,271
Equity funds subtotal	5,104		4,162
Balanced funds - commingled funds	273
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	967		882
Debt securities issued by states of the United States and political subdivisions of the states	429		294
Debt securities issued by foreign governments	105		87
Corporate debt securities	2,236		1,784
Federal agency mortgage-backed securities	79		10
Commercial mortgage-backed securities (non-agency)	39		40
Residential mortgage-backed securities (non-agency)	3		7
Mutual funds	21		18
Commingled funds	328
Fixed income subtotal	4,207		3,122
Middle market lending	354		314
Private Equity	54		5
Other debt obligations	19		14
Fair Value Assets Measured On Recurring Basis Real Estate	1
Nuclear decommissioning trust fund investments subtotal	10,335		8,076
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	14		(5)
Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	12		26
Equity
Individually held	7		16
Equity funds subtotal	7		16
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	15		49
Debt securities issued by states of the United States and political subdivisions of the states	19		20
Corporate debt securities	138		227
Commingled funds	4
Fixed income subtotal	176		296
Middle market lending	166		112
Other debt obligations			1
Pledged assets for Zion Station decommissioning subtotal	361		451
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	4		7
Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents			2
Fixed income
Mutual funds	46		54
Rabbi trust investments subtotal	46		56
Deferred compensation obligation	(45)		(53)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	(45)		(53)
Supplemental executive retirement plan fair value	1		1
Cash surrender value of life insurance investments excluded from Rabbi Trust investments	35		32
Commodity Mark To Market Derivative Assets [Member]
Fixed income
Economic hedges	4,602		3,960
Proprietary trading	880		1,761
Effect of netting and allocation of collateral	4,248		4,424
Commodity derivative assets subtotal	1,234		1,297
Commodity Mark To Market Derivative Liabilities [Member]
Fixed income
Economic hedges	(4,324)		(3,020)
Proprietary trading	(891)		(1,703)
Effect of netting and allocation of collateral	(4,707)		(4,280)
Commodity derivative assets subtotal	(508)		(443)
Interest Rate Mark To Market Derivative Assets [Member]
Fixed income
Effect of netting and allocation of collateral	(24)		(32)
Interest rate and foreign currency derivative assets			(69)
Interest rate and foreign currency derivative assets subtotal	(34)		(37)
Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income
Effect of netting and allocation of collateral	(22)		(32)
Interest rate and foreign currency derivative assets			(48)
Interest rate and foreign currency derivative assets subtotal	(32)		(16)
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	1,876		1,230
Fixed income
Other investments	13		0
Total assets	5,881		4,533
Deferred compensation obligation	0		0
Total liabilities	0		1
Total net assets	5,881		4,534
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0		0
Collateral received from counterparties, net of collateral paid to counterparties	28		6
Fair Value, Inputs, Level 1 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	261		459
Equity
Individually held	2,569		1,776
Exchange traded funds	170		115
Commingled funds	0		0
Equity funds subtotal	2,739		1,891
Balanced funds - commingled funds	0
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	967		882
Debt securities issued by states of the United States and political subdivisions of the states	0		0
Debt securities issued by foreign governments	0		0
Corporate debt securities	0		0
Federal agency mortgage-backed securities	0		0
Commercial mortgage-backed securities (non-agency)	0		0
Residential mortgage-backed securities (non-agency)	0		0
Mutual funds	0		0
Commingled funds	0
Fixed income subtotal	967		882
Middle market lending	0		0
Private Equity	0		0
Other debt obligations	0		0
Fair Value Assets Measured On Recurring Basis Real Estate	0
Nuclear decommissioning trust fund investments subtotal	3,967		3,232
Fair Value, Inputs, Level 1 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Equity
Individually held	5		16
Equity funds subtotal	5		16
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	13		45
Debt securities issued by states of the United States and political subdivisions of the states	0		0
Corporate debt securities	0		0
Commingled funds	0
Fixed income subtotal	13		45
Middle market lending	0		0
Other debt obligations			0
Pledged assets for Zion Station decommissioning subtotal	18		61
Fair Value, Inputs, Level 1 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents			2
Fixed income
Mutual funds	46		54
Rabbi trust investments subtotal	46		56
Fair Value, Inputs, Level 1 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income
Economic hedges	396		493
Proprietary trading	129		324
Effect of netting and allocation of collateral	563		863
Commodity derivative assets subtotal	(38)		(46)
Fair Value, Inputs, Level 1 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income
Economic hedges	(458)		(540)
Proprietary trading	(133)		(328)
Effect of netting and allocation of collateral	(591)		(869)
Commodity derivative assets subtotal	0		1
Fair Value, Inputs, Level 1 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income
Effect of netting and allocation of collateral	(19)		(30)
Interest rate and foreign currency derivative assets			(30)
Interest rate and foreign currency derivative assets subtotal	1		0
Fair Value, Inputs, Level 1 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income
Effect of netting and allocation of collateral	(17)		(31)
Interest rate and foreign currency derivative assets			(31)
Interest rate and foreign currency derivative assets subtotal	0		0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Fixed income
Other investments	0		0
Total assets	6,524		5,575
Deferred compensation obligation	(105)		(114)
Total liabilities	(214)		(269)
Total net assets	6,310		5,306
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	(105)		(114)
Collateral received from counterparties, net of collateral paid to counterparties	200		(124)
Fair Value, Inputs, Level 2 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	62		0
Equity
Individually held	0		0
Exchange traded funds	0		0
Commingled funds	2,365		2,271
Equity funds subtotal	2,365		2,271
Balanced funds - commingled funds	273
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	0		0
Debt securities issued by states of the United States and political subdivisions of the states	429		294
Debt securities issued by foreign governments	105		87
Corporate debt securities	2,001		1,753
Federal agency mortgage-backed securities	79		10
Commercial mortgage-backed securities (non-agency)	39		40
Residential mortgage-backed securities (non-agency)	3		7
Mutual funds	21		18
Commingled funds	328
Fixed income subtotal	3,005		2,209
Middle market lending	0		0
Private Equity	0		0
Other debt obligations	19		14
Fair Value Assets Measured On Recurring Basis Real Estate	0
Nuclear decommissioning trust fund investments subtotal	5,724		4,494
Fair Value, Inputs, Level 2 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	12		26
Equity
Individually held	2		0
Equity funds subtotal	2		0
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	2		4
Debt securities issued by states of the United States and political subdivisions of the states	19		20
Corporate debt securities	138		227
Commingled funds	4
Fixed income subtotal	163		251
Middle market lending	0		0
Other debt obligations			1
Pledged assets for Zion Station decommissioning subtotal	177		278
Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents			0
Fixed income
Mutual funds	0		0
Rabbi trust investments subtotal	0		0
Fair Value, Inputs, Level 2 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income
Economic hedges	2,523		2,582
Proprietary trading	537		1,315
Effect of netting and allocation of collateral	2,472		3,131
Commodity derivative assets subtotal	588		766
Fair Value, Inputs, Level 2 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income
Economic hedges	(2,194)		(1,890)
Proprietary trading	(555)		(1,256)
Effect of netting and allocation of collateral	(2,672)		(3,007)
Commodity derivative assets subtotal	(77)		(139)
Fair Value, Inputs, Level 2 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income
Effect of netting and allocation of collateral	(5)		(2)
Interest rate and foreign currency derivative assets			(39)
Interest rate and foreign currency derivative assets subtotal	(35)		(37)
Fair Value, Inputs, Level 2 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income
Effect of netting and allocation of collateral	(5)		(1)
Interest rate and foreign currency derivative assets			(17)
Interest rate and foreign currency derivative assets subtotal	(32)		(16)
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Fixed income
Other investments	3		15
Total assets	1,497		1,054
Deferred compensation obligation	0		0
Total liabilities	(431)		(305)
Total net assets	1,066		749
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0		0
Collateral received from counterparties, net of collateral paid to counterparties	231		(26)
Fair Value, Inputs, Level 3 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Equity
Individually held	0		0
Exchange traded funds	0		0
Commingled funds	0		0
Equity funds subtotal	0		0
Balanced funds - commingled funds	0
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	0		0
Debt securities issued by states of the United States and political subdivisions of the states	0		0
Debt securities issued by foreign governments	0		0
Corporate debt securities	235		31
Federal agency mortgage-backed securities	0		0
Commercial mortgage-backed securities (non-agency)	0		0
Residential mortgage-backed securities (non-agency)	0		0
Mutual funds	0		0
Commingled funds	0
Fixed income subtotal	235		31
Middle market lending	354		314
Private Equity	54		5
Other debt obligations	0		0
Fair Value Assets Measured On Recurring Basis Real Estate	1
Nuclear decommissioning trust fund investments subtotal	644		350
Fair Value, Inputs, Level 3 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Equity
Individually held	0		0
Equity funds subtotal	0		0
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	0		0
Debt securities issued by states of the United States and political subdivisions of the states	0		0
Corporate debt securities	0		0
Commingled funds	0
Fixed income subtotal	0		0
Middle market lending	166		112
Other debt obligations			0
Pledged assets for Zion Station decommissioning subtotal	166		112
Fair Value, Inputs, Level 3 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents			0
Fixed income
Mutual funds	0		0
Rabbi trust investments subtotal	0		0
Fair Value, Inputs, Level 3 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income
Economic hedges	1,683		885
Proprietary trading	214		122
Effect of netting and allocation of collateral	1,213		430
Commodity derivative assets subtotal	684		577
Fair Value, Inputs, Level 3 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income
Economic hedges	(1,672)		(590)
Proprietary trading	(203)		(119)
Effect of netting and allocation of collateral	(1,444)		(404)
Commodity derivative assets subtotal	(431)		(305)
Fair Value, Inputs, Level 3 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income
Effect of netting and allocation of collateral	0		0
Interest rate and foreign currency derivative assets			0
Interest rate and foreign currency derivative assets subtotal	0		0
Fair Value, Inputs, Level 3 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income
Effect of netting and allocation of collateral	0		0
Interest rate and foreign currency derivative assets			0
Interest rate and foreign currency derivative assets subtotal	0		0
Designated as Hedging Instrument [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	25
Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	25
Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(12)
Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(12)
Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
Derivative [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	12
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Mark-to-market derivative liabilities	265		285
Derivative Liability, Current	243		158
Derivative [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Derivative [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	12
Derivative [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Derivative [Member] | Derivative Financial Instruments, Liabilities [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(22)
Derivative [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
Derivative [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(22)
Derivative [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
Interest Rate Swap [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	21
Interest Rate Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	18
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	3
Interest Rate Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(20)
Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(17)
Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(3)
Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
Exelon Generation Co L L C [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	944		1,006
Fixed income
Other investments	16		15
Total assets	12,922		10,888
Deferred compensation obligation	(29)		(29)
Total liabilities	(368)		(291)
Total net assets	12,554		10,597
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	(29)		(29)
Mark-to-market derivative liabilities	104		120
Derivative Liability, Current	235		142
Exelon Generation Co L L C [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	323		459
Equity
Individually held	2,569		1,776
Exchange traded funds	170		115
Commingled funds	2,365		2,271
Equity funds subtotal	5,104		4,162
Balanced funds - commingled funds	273
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	967		882
Debt securities issued by states of the United States and political subdivisions of the states	429		294
Debt securities issued by foreign governments	105		87
Corporate debt securities	2,236		1,784
Federal agency mortgage-backed securities	79		10
Commercial mortgage-backed securities (non-agency)	39		40
Residential mortgage-backed securities (non-agency)	3		7
Mutual funds	21		18
Commingled funds	328
Fixed income subtotal	4,207		3,122
Middle market lending	354		314
Private Equity	54		5
Other debt obligations	19		14
Fair Value Assets Measured On Recurring Basis Real Estate	1
Nuclear decommissioning trust fund investments subtotal	10,335		8,076
Exelon Generation Co L L C [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	12		26
Equity
Individually held	7		16
Equity funds subtotal	7		16
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	15		49
Debt securities issued by states of the United States and political subdivisions of the states	19		20
Corporate debt securities	138		227
Commingled funds	4
Fixed income subtotal	176		296
Middle market lending	166		112
Other debt obligations			1
Pledged assets for Zion Station decommissioning subtotal	361		451
Exelon Generation Co L L C [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents			0
Fixed income
Mutual funds	15		13
Rabbi trust investments subtotal	15		13
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash surrender value of life insurance investments excluded from Rabbi Trust investments	11		10
Exelon Generation Co L L C [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income
Economic hedges	4,602		3,960
Proprietary trading	880		1,761
Effect of netting and allocation of collateral	4,248		4,424
Commodity derivative assets subtotal	1,234		1,297
Exelon Generation Co L L C [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income
Economic hedges	(4,146)		(2,827)
Proprietary trading	(891)		(1,703)
Effect of netting and allocation of collateral	(4,707)		(4,280)
Commodity derivative assets subtotal	(330)		(250)
Exelon Generation Co L L C [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income
Effect of netting and allocation of collateral	(24)		(32)
Interest rate and foreign currency derivative assets			(62)
Interest rate and foreign currency derivative assets subtotal	(17)		(30)
Exelon Generation Co L L C [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income
Effect of netting and allocation of collateral	(22)		(32)
Interest rate and foreign currency derivative assets			(44)
Interest rate and foreign currency derivative assets subtotal	(9)		(12)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	944		1,006
Fixed income
Other investments	13		0
Total assets	4,918		4,266
Deferred compensation obligation	0		0
Total liabilities	0		1
Total net assets	4,918		4,267
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	261		459
Equity
Individually held	2,569		1,776
Exchange traded funds	170		115
Commingled funds	0		0
Equity funds subtotal	2,739		1,891
Balanced funds - commingled funds	0
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	967		882
Debt securities issued by states of the United States and political subdivisions of the states	0		0
Debt securities issued by foreign governments	0		0
Corporate debt securities	0		0
Federal agency mortgage-backed securities	0		0
Commercial mortgage-backed securities (non-agency)	0		0
Residential mortgage-backed securities (non-agency)	0		0
Mutual funds	0		0
Commingled funds	0
Fixed income subtotal	967		882
Middle market lending	0		0
Private Equity	0		0
Other debt obligations	0		0
Fair Value Assets Measured On Recurring Basis Real Estate	0
Nuclear decommissioning trust fund investments subtotal	3,967		3,232
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Equity
Individually held	5		16
Equity funds subtotal	5		16
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	13		45
Debt securities issued by states of the United States and political subdivisions of the states	0		0
Corporate debt securities	0		0
Commingled funds	0
Fixed income subtotal	13		45
Middle market lending	0		0
Other debt obligations			0
Pledged assets for Zion Station decommissioning subtotal	18		61
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents			0
Fixed income
Mutual funds	15		13
Rabbi trust investments subtotal	15		13
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income
Economic hedges	396		493
Proprietary trading	129		324
Effect of netting and allocation of collateral	563		863
Commodity derivative assets subtotal	(38)		(46)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income
Economic hedges	(458)		(540)
Proprietary trading	(133)		(328)
Effect of netting and allocation of collateral	(591)		(869)
Commodity derivative assets subtotal	0		1
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income
Effect of netting and allocation of collateral	(19)		(30)
Interest rate and foreign currency derivative assets			(30)
Interest rate and foreign currency derivative assets subtotal	1		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income
Effect of netting and allocation of collateral	(17)		(31)
Interest rate and foreign currency derivative assets			(31)
Interest rate and foreign currency derivative assets subtotal	0		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Equity
Exchange traded funds			0
Commingled funds			2,271
Equity funds subtotal			2,271
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies			0
Debt securities issued by states of the United States and political subdivisions of the states			294
Debt securities issued by foreign governments			87
Corporate debt securities			1,753
Federal agency mortgage-backed securities			10
Commercial mortgage-backed securities (non-agency)			40
Residential mortgage-backed securities (non-agency)			7
Mutual funds			18
Fixed income subtotal			2,209
Middle market lending			0
Private Equity			0
Other debt obligations			14
Nuclear decommissioning trust fund investments subtotal			4,494
Other investments	0		0
Total assets	6,507		5,568
Deferred compensation obligation	(29)		(29)
Total liabilities	(115)		(180)
Total net assets	6,392		5,388
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	(29)		(29)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	62		0
Equity
Individually held	0		0
Exchange traded funds	0
Commingled funds	2,365
Equity funds subtotal	2,365
Balanced funds - commingled funds	273
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	0
Debt securities issued by states of the United States and political subdivisions of the states	429
Debt securities issued by foreign governments	105
Corporate debt securities	2,001
Federal agency mortgage-backed securities	79
Commercial mortgage-backed securities (non-agency)	39
Residential mortgage-backed securities (non-agency)	3
Mutual funds	21
Commingled funds	328
Fixed income subtotal	3,005
Middle market lending	0
Private Equity	0
Other debt obligations	19
Fair Value Assets Measured On Recurring Basis Real Estate	0
Nuclear decommissioning trust fund investments subtotal	5,724
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	12		26
Equity
Individually held	2		0
Equity funds subtotal	2		0
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	2		4
Debt securities issued by states of the United States and political subdivisions of the states	19		20
Corporate debt securities	138		227
Commingled funds	4
Fixed income subtotal	163		251
Middle market lending	0		0
Other debt obligations			1
Pledged assets for Zion Station decommissioning subtotal	177		278
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents			0
Fixed income
Mutual funds	0		0
Rabbi trust investments subtotal	0		0
Commodity derivative assets subtotal			766
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income
Economic hedges	2,523		2,582
Proprietary trading	537		1,315
Effect of netting and allocation of collateral	2,472		3,131
Commodity derivative assets subtotal	588
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income
Economic hedges	(2,194)		(1,890)
Proprietary trading	(555)		(1,256)
Effect of netting and allocation of collateral	(2,672)		(3,007)
Commodity derivative assets subtotal	(77)		(139)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income
Effect of netting and allocation of collateral	(5)		(2)
Interest rate and foreign currency derivative assets			(32)
Interest rate and foreign currency derivative assets subtotal	(18)		(30)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income
Effect of netting and allocation of collateral	(5)		(1)
Interest rate and foreign currency derivative assets			(13)
Interest rate and foreign currency derivative assets subtotal	(9)		(12)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Fixed income
Other investments	3		15
Total assets	1,497		1,054
Deferred compensation obligation	0		0
Total liabilities	(253)		(112)
Total net assets	1,244		942
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Equity
Individually held	0		0
Exchange traded funds	0		0
Commingled funds	0		0
Equity funds subtotal	0		0
Balanced funds - commingled funds	0
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	0		0
Debt securities issued by states of the United States and political subdivisions of the states	0		0
Debt securities issued by foreign governments	0		0
Corporate debt securities	235		31
Federal agency mortgage-backed securities	0		0
Commercial mortgage-backed securities (non-agency)	0		0
Residential mortgage-backed securities (non-agency)	0		0
Mutual funds	0		0
Commingled funds	0
Fixed income subtotal	235		31
Middle market lending	354		314
Private Equity	54		5
Other debt obligations	0		0
Fair Value Assets Measured On Recurring Basis Real Estate	1
Nuclear decommissioning trust fund investments subtotal	644		350
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Equity
Individually held	0		0
Equity funds subtotal	0		0
Fixed income
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	0		0
Debt securities issued by states of the United States and political subdivisions of the states	0		0
Corporate debt securities	0		0
Commingled funds	0
Fixed income subtotal	0		0
Middle market lending	166		112
Other debt obligations			0
Pledged assets for Zion Station decommissioning subtotal	166		112
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents			0
Fixed income
Mutual funds	0		0
Rabbi trust investments subtotal	0		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income
Economic hedges	1,683		885
Proprietary trading	214		122
Effect of netting and allocation of collateral	1,213		430
Commodity derivative assets subtotal	684		577
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income
Economic hedges	(1,494)		(397)
Proprietary trading	(203)		(119)
Effect of netting and allocation of collateral	(1,444)		(404)
Commodity derivative assets subtotal	(253)		(112)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income
Effect of netting and allocation of collateral	0		0
Interest rate and foreign currency derivative assets			0
Interest rate and foreign currency derivative assets subtotal	0		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income
Effect of netting and allocation of collateral	0		0
Interest rate and foreign currency derivative assets			0
Interest rate and foreign currency derivative assets subtotal	0		0
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	13
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	13
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(2)
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(2)
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
Exelon Generation Co L L C [Member] | Derivative [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	7
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Mark-to-market derivative liabilities	101	[1]	109	[2]
Derivative Liability, Current	229	[1]	141	[2]
Exelon Generation Co L L C [Member] | Derivative [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Exelon Generation Co L L C [Member] | Derivative [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	7
Exelon Generation Co L L C [Member] | Derivative [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Exelon Generation Co L L C [Member] | Derivative [Member] | Derivative Financial Instruments, Liabilities [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(9)
Exelon Generation Co L L C [Member] | Derivative [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
Exelon Generation Co L L C [Member] | Derivative [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(9)
Exelon Generation Co L L C [Member] | Derivative [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	21
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Current	1
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	18
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	3
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed income
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(20)
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(17)
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(3)
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed income
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
PECO Energy Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	304		175
Fixed income
Commodity derivative assets subtotal	0		0
Total assets	313		184
Deferred compensation obligation	(15)		(17)
Total liabilities	(15)		(17)
Total net assets	298		167
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	(15)		(17)
Cash surrender value of life insurance investments excluded from Rabbi Trust investments	14		14
PECO Energy Co [Member] | Rabbi Trust Investments [Member]
Fixed income
Mutual funds	9		9
Rabbi trust investments subtotal	9		9
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	304		175
Fixed income
Commodity derivative assets subtotal	0		0
Total assets	313		184
Deferred compensation obligation	0		0
Total liabilities	0		0
Total net assets	313		184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0		0
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Rabbi Trust Investments [Member]
Fixed income
Mutual funds	9		9
Rabbi trust investments subtotal	9		9
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Fixed income
Commodity derivative assets subtotal	0		0
Total assets	0		0
Deferred compensation obligation	(15)		(17)
Total liabilities	(15)		(17)
Total net assets	(15)		(17)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	(15)		(17)
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fixed income
Mutual funds	0		0
Rabbi trust investments subtotal	0		0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Fixed income
Commodity derivative assets subtotal	0		0
Total assets	0		0
Deferred compensation obligation	0		0
Total liabilities	0		0
Total net assets	0		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0		0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Rabbi Trust Investments [Member]
Fixed income
Mutual funds	0		0
Rabbi trust investments subtotal	0		0
Commonwealth Edison Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Fixed income
Commodity derivative assets subtotal	178		193
Total assets	0		5
Deferred compensation obligation	(8)		(8)
Total liabilities	(186)		(201)
Total net assets	(186)		(196)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	(8)		(8)
Mark-to-market derivative liabilities	164		176
Derivative Liability, Current	14		17
Commonwealth Edison Co [Member] | Rabbi Trust Investments [Member]
Fixed income
Mutual funds	0		5
Rabbi trust investments subtotal	0		5
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Fixed income
Commodity derivative assets subtotal	0		0
Total assets	0		5
Deferred compensation obligation	0		0
Total liabilities	0		0
Total net assets	0		5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0		0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Rabbi Trust Investments [Member]
Fixed income
Mutual funds	0		5
Rabbi trust investments subtotal	0		5
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Fixed income
Commodity derivative assets subtotal	0		0
Total assets	0		0
Deferred compensation obligation	(8)		(8)
Total liabilities	(8)		(8)
Total net assets	(8)		(8)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	(8)		(8)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fixed income
Mutual funds	0		0
Rabbi trust investments subtotal	0		0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Fixed income
Commodity derivative assets subtotal	178		193
Total assets	0		0
Deferred compensation obligation	0		0
Total liabilities	(178)		(193)
Total net assets	(178)		(193)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0		0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Rabbi Trust Investments [Member]
Fixed income
Mutual funds	0		0
Rabbi trust investments subtotal	0		0
Baltimore Gas and Electric Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	5		31
Fixed income
Commodity derivative assets subtotal	0		0
Total assets	10		37
Deferred compensation obligation	(5)		0
Total liabilities	(5)		(6)
Total net assets	5		31
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	(5)		0
Baltimore Gas and Electric Company [Member] | Rabbi Trust Investments [Member]
Fixed income
Mutual funds	5		6
Rabbi trust investments subtotal	5		6
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	5		31
Fixed income
Commodity derivative assets subtotal	0		0
Total assets	10		37
Deferred compensation obligation	0		0
Total liabilities	0		0
Total net assets	10		37
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0		0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Rabbi Trust Investments [Member]
Fixed income
Mutual funds	5		6
Rabbi trust investments subtotal	5		6
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Fixed income
Commodity derivative assets subtotal	0		0
Total assets	0		0
Deferred compensation obligation	(5)		(6)
Total liabilities	(5)		(6)
Total net assets	(5)		(6)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	(5)		(6)
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fixed income
Mutual funds	0		0
Rabbi trust investments subtotal	0		0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0		0
Fixed income
Commodity derivative assets subtotal	0		0
Total assets	0		0
Deferred compensation obligation	0		0
Total liabilities	0		0
Total net assets	0		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0		0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Rabbi Trust Investments [Member]
Fixed income
Mutual funds	0		0
Rabbi trust investments subtotal	$ 0		$ 0

[1] Current and noncurrent assets are shown net of collateral of $(96) million and $(50) million, respectively, and current and noncurrent liabilities are shown net of collateral of $(205) million and $(108) million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $459 million at September 30, 2014.

[2] Current and noncurrent assets are shown net of collateral of $84 million and $72 million, respectively, and current and noncurrent liabilities are shown net of collateral of $(12) million and $0 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $144 million at December 31, 2013.