Fair Value of Financial Assets and Liabilities (Fair Value Measurements, Recurring and Nonrecurring) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013		Jun. 30, 2013
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	$ 1,034	[1]	$ 1,230	[1]
Fixed income [Abstract]
Other investments	23		15
Deferred compensation	(104)		(114)
Total assets	13,031		11,162
Total liabilities	(594)		(573)
Total net assets	12,437		10,589
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	104		114
Mark-to-market derivative liabilities (current liabilities)	228		159
Mark-to-market derivative liabilities (noncurrent liabilities)	262		300
Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	217		459
Equity Securities [Abstract]
Equity securities	2,572		1,776
Exchange traded funds	164		115
Commingled funds	2,529		2,271
Equity securities subtotal	5,265
Balanced Funds - Commingled Funds	273
Fixed income [Abstract]
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	990		882
Debt securities issued by states of the United States and political subdivisions of the states	416		294
Debt securities issued by foreign governments	114		87
Corporate debt securities	2,240		1,784
Federal agency mortgage-backed securities	84		10
Commercial mortgage-backed securities (non-agency)	43		40
Residential mortgage-backed securities (non-agency)	3		7
Commingled funds fixed income	325
Mutual funds fixed income	18		18
Fixed income subtotal	4,233		3,122
Private equity	35		5
Direct lending securities	376		314
Other debt obligations	24		14
Nuclear decommissioning trust fund investments subtotal	10,423	[2]	8,076	[2]
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 And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	45		26
Equity Securities [Abstract]
Equity securities	6		16
Equity securities subtotal	6		16
Fixed income [Abstract]
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	172		227
Commingled funds fixed income	5
Fixed income subtotal	211		296
Direct lending securities	133		112
Other debt obligations			1
Pledged assets for Zion Station decommissioning subtotal	395	[3]	451	[3]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Net assets (liabilities) excluded from pledged assets	7		7
Rabbi Trust Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	2		2
Equity Securities [Abstract]
Equity securities subtotal	0
Fixed income [Abstract]
Mutual funds	43	[4],[5]	54	[4],[5]
Rabbi trust investments subtotal	45		56
Deferred compensation	(42)		(53)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	42		53
Supplemental executive retirement plan fair value	1		1
Cash surrender value of life insurance investments excluded from Rabbi Trust investments	34		32
Derivative Financial Instruments Liabilities [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Fair value of energy swap contract current liability	13		17
Fair value of energy swap contract noncurrent liability	121		176
Commodity Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Other derivatives	4,816		3,960
Proprietary trading	1,074		1,761
Effect of netting and allocation of collateral received/(paid)	(4,815)	[6]	(4,424)	[6]
Mark-to-market subtotal	1,075		1,297
Commodity Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Other derivatives	(4,702)		(3,020)
Proprietary trading	(1,065)		(1,703)
Effect of netting and allocation of collateral received/(paid)	5,305	[6]	4,280	[6]
Mark-to-market subtotal	(462)		(443)
Interest Rate Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)	(28)		32
Interest rate mark to market	64		69
Interest rate mark-to-market Subtotal	36		37
Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)	(30)		32
Interest rate mark to market	(58)		48
Interest rate mark-to-market Subtotal	(28)		16
Fair Value Inputs Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	1,034	[1]	1,230	[1]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)			(31)
Other investments	13		0
Deferred compensation	0		0
Total assets	5,031		4,533
Total liabilities	2		1
Total net assets	5,033		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	49		6
Fair Value Inputs Level 1 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	151		459
Equity Securities [Abstract]
Equity securities	2,572		1,776
Exchange traded funds	164		115
Commingled funds	0
Equity securities subtotal	2,736		1,891
Fixed income [Abstract]
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	990		882
Debt securities issued by states of the United States and political subdivisions of the states	0
Debt securities issued by foreign governments	0
Corporate debt securities	0
Federal agency mortgage-backed securities	0
Commercial mortgage-backed securities (non-agency)	0
Residential mortgage-backed securities (non-agency)	0
Mutual funds fixed income	0
Fixed income subtotal	990		882
Direct lending securities	0
Other debt obligations	0
Nuclear decommissioning trust fund investments subtotal	3,877	[2]	3,232	[2]
Fair Value Inputs Level 1 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Equity Securities [Abstract]
Equity securities	4		16
Equity securities subtotal	4		16
Fixed income [Abstract]
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	12		45
Debt securities issued by states of the United States and political subdivisions of the states	0
Corporate debt securities	0
Fixed income subtotal	12		45
Direct lending securities	0
Pledged assets for Zion Station decommissioning subtotal	16	[3]	61	[3]
Fair Value Inputs Level 1 [Member] | Rabbi Trust Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	2		2
Fixed income [Abstract]
Mutual funds	43	[4],[5]	54	[4],[5]
Rabbi trust investments subtotal	45		56
Fair Value Inputs Level 1 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Other derivatives	434		493
Proprietary trading	178		324
Effect of netting and allocation of collateral received/(paid)	(569)	[6]	(863)	[6]
Mark-to-market subtotal	43		(46)
Fair Value Inputs Level 1 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Other derivatives	(434)		(540)
Proprietary trading	(182)		(328)
Effect of netting and allocation of collateral received/(paid)	618	[6]	869	[6]
Mark-to-market subtotal	2		1
Fair Value Inputs Level 1 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)	(21)		(30)
Interest rate mark to market	24		30
Interest rate mark-to-market Subtotal	3		0
Fair Value Inputs Level 1 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)	24
Interest rate mark to market	(24)		31
Interest rate mark-to-market Subtotal	0		0
Fair Value Inputs Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	0	[1]	0	[1]
Fixed income [Abstract]
Deferred compensation	(104)		(114)
Total assets	6,795		5,575
Total liabilities	(234)		(269)
Total net assets	6,561		5,306
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	104		114
Collateral received from counterparties, net of collateral paid to counterparties	289		(124)
Fair Value Inputs Level 2 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	66
Equity Securities [Abstract]
Equity securities	0
Commingled funds	2,529		2,271
Equity securities subtotal	2,529		2,271
Balanced Funds - Commingled Funds	273
Fixed income [Abstract]
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	416		294
Debt securities issued by foreign governments	114		87
Corporate debt securities	2,059		1,753
Federal agency mortgage-backed securities	84		10
Commercial mortgage-backed securities (non-agency)	43		40
Residential mortgage-backed securities (non-agency)	3		7
Commingled funds fixed income	325
Mutual funds fixed income	18		18
Fixed income subtotal	3,062		2,209
Direct lending securities	0
Other debt obligations	24		14
Nuclear decommissioning trust fund investments subtotal	5,954	[2]	4,494	[2]
Fair Value Inputs Level 2 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	45		26
Equity Securities [Abstract]
Equity securities	2
Equity securities subtotal	2		0
Fixed income [Abstract]
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	3		4
Debt securities issued by states of the United States and political subdivisions of the states	19		20
Corporate debt securities	172		227
Commingled funds fixed income	5
Fixed income subtotal	199		251
Direct lending securities	0
Other debt obligations			1
Pledged assets for Zion Station decommissioning subtotal	246	[3]	278	[3]
Fair Value Inputs Level 2 [Member] | Rabbi Trust Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	0
Fixed income [Abstract]
Mutual funds	0	[4],[5]
Rabbi trust investments subtotal	0		0
Fair Value Inputs Level 2 [Member] | Derivative Financial Instruments Assets [Member]
Fixed income [Abstract]
Other investments	0
Fair Value Inputs Level 2 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Other derivatives	2,969		2,582
Proprietary trading	712		1,315
Effect of netting and allocation of collateral received/(paid)	(3,119)	[6]	(3,131)	[6]
Mark-to-market subtotal	562		766
Fair Value Inputs Level 2 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Other derivatives	(2,803)		(1,890)
Proprietary trading	(707)		(1,256)
Effect of netting and allocation of collateral received/(paid)	3,408	[6]	3,007	[6]
Mark-to-market subtotal	(102)		(139)
Fair Value Inputs Level 2 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)	(7)		2
Interest rate mark to market	40		39
Interest rate mark-to-market Subtotal	33		37
Fair Value Inputs Level 2 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)	(6)		(1)
Interest rate mark to market	(34)		17
Interest rate mark-to-market Subtotal	(28)		16
Fair Value Inputs Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	0	[1]	0	[1]
Fixed income [Abstract]
Other investments	10		15
Deferred compensation	0		0
Total assets	1,205		1,054
Total liabilities	(362)		(305)
Total net assets	843		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	152		(26)
Fair Value Inputs Level 3 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	0
Equity Securities [Abstract]
Equity securities	0		0
Commingled funds	0
Equity securities subtotal	0
Fixed income [Abstract]
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	0
Debt securities issued by foreign governments	0
Corporate debt securities	181		31
Federal agency mortgage-backed securities	0
Commercial mortgage-backed securities (non-agency)	0
Residential mortgage-backed securities (non-agency)	0
Mutual funds fixed income	0
Fixed income subtotal	181		31
Private equity	35		5
Direct lending securities	376		314
Other debt obligations	0
Nuclear decommissioning trust fund investments subtotal	592	[2]	350	[2]
Fair Value Inputs Level 3 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Equity Securities [Abstract]
Equity securities subtotal			0
Fixed income [Abstract]
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	0
Corporate debt securities	0
Fixed income subtotal	0		0
Direct lending securities	133		112
Pledged assets for Zion Station decommissioning subtotal	133	[3]	112	[3]
Fair Value Inputs Level 3 [Member] | Rabbi Trust Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	0
Fixed income [Abstract]
Mutual funds	0	[4],[5]
Rabbi trust investments subtotal	0		0
Fair Value Inputs Level 3 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Other derivatives	1,413		885
Proprietary trading	184		122
Effect of netting and allocation of collateral received/(paid)	(1,127)	[6]	(430)	[6]
Mark-to-market subtotal	470		577
Fair Value Inputs Level 3 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Other derivatives	(1,465)		(590)
Proprietary trading	(176)		(119)
Effect of netting and allocation of collateral received/(paid)	1,279	[6]	404	[6]
Mark-to-market subtotal	(362)		(305)
Fair Value Inputs Level 3 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Interest rate mark to market	0
Interest rate mark-to-market Subtotal	0		0
Fair Value Inputs Level 3 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Interest rate mark to market	0
Interest rate mark-to-market Subtotal	0		0
Exelon Generation Co L L C [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	65		1,006	[1]
Fixed income [Abstract]
Other investments	23		15
Deferred compensation	(29)		(29)
Total assets	12,014		10,888
Total liabilities	(379)		(291)
Total net assets	11,635		10,597
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	29		29
Mark-to-market derivative liabilities (current liabilities)	215		142
Mark-to-market derivative liabilities (noncurrent liabilities)	135		120
Exelon Generation Co L L C [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	217		459
Equity Securities [Abstract]
Equity securities	2,572		1,776
Exchange traded funds	164		115
Commingled funds	2,529		2,271
Equity securities subtotal	5,265		4,162
Balanced Funds - Commingled Funds	273
Fixed income [Abstract]
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	990		882
Debt securities issued by states of the United States and political subdivisions of the states	416		294
Debt securities issued by foreign governments	114		87
Corporate debt securities	2,240		1,784
Federal agency mortgage-backed securities	84		10
Commercial mortgage-backed securities (non-agency)	43		40
Residential mortgage-backed securities (non-agency)	3		7
Commingled funds fixed income	325
Mutual funds fixed income	18		18
Fixed income subtotal	4,233		3,122
Private equity	35		5
Direct lending securities	376		314
Other debt obligations	24		14
Nuclear decommissioning trust fund investments subtotal	10,423	[2]	8,076	[2]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	14		(5)
Exelon Generation Co L L C [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	45		26
Equity Securities [Abstract]
Equity securities	6		16
Equity securities subtotal	6		16
Fixed income [Abstract]
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	172		227
Commingled funds fixed income	5
Fixed income subtotal	211		296
Direct lending securities	133		112
Other debt obligations			1
Pledged assets for Zion Station decommissioning subtotal	395	[3]	451	[3]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	7		7
Exelon Generation Co L L C [Member] | Rabbi Trust Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	1		0
Fixed income [Abstract]
Mutual funds	14	[7]	13	[7]
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	10		10
Exelon Generation Co L L C [Member] | Derivative Financial Instruments Assets [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Fair value swap contract current asset	0		0
Fair value swap contract noncurrent asset	0		0
Exelon Generation Co L L C [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Other derivatives	4,816		3,960
Proprietary trading	1,074		1,761
Effect of netting and allocation of collateral received/(paid)	(4,815)	[6]	(4,424)	[6]
Mark-to-market subtotal	1,075		1,297
Exelon Generation Co L L C [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Cash flow hedges	0
Other derivatives	(4,568)		(2,827)
Proprietary trading	(1,065)		(1,703)
Effect of netting and allocation of collateral received/(paid)	5,305	[6]	4,280	[6]
Mark-to-market subtotal	(328)		(250)
Exelon Generation Co L L C [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)	28		32
Interest rate mark to market	46		62
Interest rate mark-to-market Subtotal	18		30
Exelon Generation Co L L C [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)	(30)		(32)
Interest rate mark to market	(52)		(44)
Interest rate mark-to-market Subtotal	(22)		(12)
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	65		1,006	[1]
Fixed income [Abstract]
Other investments	13		0
Deferred compensation	0
Total assets	4,032		4,266
Total liabilities	2		1
Total net assets	4,034		4,267
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0
Collateral received from counterparties, net of collateral paid to counterparties	49		6
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 1 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	151		459
Equity Securities [Abstract]
Equity securities	2,572		1,776
Exchange traded funds	164		115
Commingled funds	0
Equity securities subtotal	2,736				1,891
Fixed income [Abstract]
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	990		882
Debt securities issued by states of the United States and political subdivisions of the states	0
Fixed income subtotal	990		882
Other debt obligations	0
Nuclear decommissioning trust fund investments subtotal	3,877	[2]	3,232	[2]
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 1 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Equity Securities [Abstract]
Equity securities	4		16
Equity securities subtotal	4		16
Fixed income [Abstract]
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	12		45
Fixed income subtotal	12		45
Pledged assets for Zion Station decommissioning subtotal	16	[3]	61	[3]
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 1 [Member] | Rabbi Trust Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	1		0
Fixed income [Abstract]
Mutual funds	14	[7]	13	[7]
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 [Abstract]
Other derivatives	434		493
Proprietary trading	178		324
Effect of netting and allocation of collateral received/(paid)	(569)	[6]	(863)	[6]
Mark-to-market subtotal	43		(46)
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 1 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Cash flow hedges	0
Other derivatives	(434)		(540)
Proprietary trading	(182)		(328)
Effect of netting and allocation of collateral received/(paid)	618	[6]	869	[6]
Mark-to-market subtotal	2		1
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 1 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)	21		30
Interest rate mark to market	24		30
Interest rate mark-to-market Subtotal	3
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 1 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)	(24)		(31)
Interest rate mark to market	(24)		(31)
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	0		0	[1]
Fixed income [Abstract]
Deferred compensation	(29)		(29)
Total assets	6,777		5,568
Total liabilities	(153)		(180)
Total net assets	6,624		5,388
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	29		29
Collateral received from counterparties, net of collateral paid to counterparties	289		(124)
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 2 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	66
Equity Securities [Abstract]
Equity securities	0
Commingled funds	2,529		2,271
Equity securities subtotal	2,529		2,271
Balanced Funds - Commingled Funds	273
Fixed income [Abstract]
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	416		294
Debt securities issued by foreign governments	114		87
Corporate debt securities	2,059		1,753
Federal agency mortgage-backed securities	84		10
Commercial mortgage-backed securities (non-agency)	43		40
Residential mortgage-backed securities (non-agency)	3		7
Commingled funds fixed income	325
Mutual funds fixed income	18		18
Fixed income subtotal	3,062		2,209
Other debt obligations	24		14
Nuclear decommissioning trust fund investments subtotal	5,954	[2]	4,494	[2]
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 2 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	45		26
Equity Securities [Abstract]
Equity securities	2
Equity securities subtotal	2		0
Fixed income [Abstract]
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	3		4
Debt securities issued by states of the United States and political subdivisions of the states	19		20
Corporate debt securities	172		227
Commingled funds fixed income	5
Fixed income subtotal	199		251
Direct lending securities	0
Other debt obligations			1
Pledged assets for Zion Station decommissioning subtotal	246	[3]	278	[3]
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 2 [Member] | Rabbi Trust Investments [Member]
Fixed income [Abstract]
Rabbi trust investments subtotal			0
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 2 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Other derivatives	2,969		2,582
Proprietary trading	712		1,315
Effect of netting and allocation of collateral received/(paid)	(3,119)	[6]	(3,131)	[6]
Mark-to-market subtotal	562		766
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 2 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Cash flow hedges	0
Other derivatives	(2,803)		(1,890)
Proprietary trading	(707)		(1,256)
Effect of netting and allocation of collateral received/(paid)	3,408	[6]	3,007	[6]
Mark-to-market subtotal	(102)		(139)
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 2 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)	7		2
Interest rate mark to market	22		32
Interest rate mark-to-market Subtotal	15		30
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 2 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Effect of netting and allocation of collateral received/(paid)	(6)		(1)
Interest rate mark to market	(28)		(13)
Interest rate mark-to-market Subtotal	(22)		(12)
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	0		0	[1]
Equity Securities [Abstract]
Equity securities	0
Fixed income [Abstract]
Other investments	10		15
Deferred compensation	0
Total assets	1,205		1,054
Total liabilities	(228)		(112)
Total net assets	977		942
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0
Collateral received from counterparties, net of collateral paid to counterparties	152		(26)
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 3 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Equity Securities [Abstract]
Commingled funds	0
Equity securities subtotal	0
Fixed income [Abstract]
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	0
Corporate debt securities	181		31
Mutual funds fixed income	0
Fixed income subtotal	181		31
Private equity	35		5
Direct lending securities	376		314
Other debt obligations	0
Nuclear decommissioning trust fund investments subtotal	592	[2]	350	[2]
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 3 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fixed income [Abstract]
Direct lending securities	133		112
Pledged assets for Zion Station decommissioning subtotal	133	[3]	112	[3]
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 3 [Member] | Rabbi Trust Investments [Member]
Fixed income [Abstract]
Rabbi trust investments subtotal			0
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 3 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fixed income [Abstract]
Other derivatives	1,413		885
Proprietary trading	184		122
Effect of netting and allocation of collateral received/(paid)	(1,127)	[6]	(430)	[6]
Mark-to-market subtotal	470		577
Exelon Generation Co L L C [Member] | Fair Value Inputs Level 3 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Cash flow hedges	0
Other derivatives	(1,331)		(397)
Proprietary trading	(176)		(119)
Effect of netting and allocation of collateral received/(paid)	1,279	[6]	404	[6]
Mark-to-market subtotal	(228)		(112)
Commonwealth Edison Co [Member]
Fixed income [Abstract]
Deferred compensation	(8)		(8)
Total assets	1		5
Total liabilities	(142)		(201)
Total net assets	(141)		(196)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	8		8
Mark-to-market derivative liabilities (current liabilities)	13		17
Mark-to-market derivative liabilities (noncurrent liabilities)	121		176
Commonwealth Edison Co [Member] | Rabbi Trust Investments [Member]
Fixed income [Abstract]
Mutual funds	1		5
Rabbi trust investments subtotal	1		5
Commonwealth Edison Co [Member] | Derivative Financial Instruments Assets [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Fair value swap contract current asset	0		0
Fair value swap contract noncurrent asset	0		0
Commonwealth Edison Co [Member] | Derivative Financial Instruments Liabilities [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Fair value of energy swap contract current liability	13		17
Fair value of energy swap contract noncurrent liability	121		176
Commonwealth Edison Co [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Mark-to-market subtotal	134	[8]	193	[8]
Commonwealth Edison Co [Member] | Fair Value Inputs Level 1 [Member]
Fixed income [Abstract]
Deferred compensation	0
Total assets	1		5
Total liabilities	0		0
Total net assets	1		5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0
Commonwealth Edison Co [Member] | Fair Value Inputs Level 1 [Member] | Rabbi Trust Investments [Member]
Fixed income [Abstract]
Mutual funds	1		5
Rabbi trust investments subtotal	1		5
Commonwealth Edison Co [Member] | Fair Value Inputs Level 1 [Member] | Derivative Financial Instruments Liabilities [Member]
Fixed income [Abstract]
Mark-to-market subtotal	0	[8]
Commonwealth Edison Co [Member] | Fair Value Inputs Level 2 [Member]
Fixed income [Abstract]
Deferred compensation	(8)		(8)
Total assets	0		0
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 [Abstract]
Mutual funds	0
Rabbi trust investments subtotal	0		0
Commonwealth Edison Co [Member] | Fair Value Inputs Level 2 [Member] | Derivative Financial Instruments Liabilities [Member]
Fixed income [Abstract]
Mark-to-market subtotal	0	[8]
Commonwealth Edison Co [Member] | Fair Value Inputs Level 3 [Member]
Fixed income [Abstract]
Deferred compensation	0
Total assets	0		0
Total liabilities	(134)		(193)
Total net assets	(134)		(193)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	0
Commonwealth Edison Co [Member] | Fair Value Inputs Level 3 [Member] | Rabbi Trust Investments [Member]
Fixed income [Abstract]
Mutual funds	0
Rabbi trust investments subtotal	0		0
Commonwealth Edison Co [Member] | Fair Value Inputs Level 3 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fixed income [Abstract]
Mark-to-market subtotal	134	[8]	193	[8]
PECO Energy Co [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	50		175
Fixed income [Abstract]
Deferred compensation	(15)		(17)
Total assets	59		184
Total liabilities	(15)		(17)
Total net assets	44		167
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	15		17
PECO Energy Co [Member] | Rabbi Trust Investments [Member]
Fixed income [Abstract]
Mutual funds	9		9
Rabbi trust investments subtotal	9	[10],[9]	9	[10],[9]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash surrender value of life insurance investments excluded from Rabbi Trust investments	14		14
PECO Energy Co [Member] | Fair Value Inputs Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	50		175
Fixed income [Abstract]
Total assets	59		184
Total net assets	59		184
PECO Energy Co [Member] | Fair Value Inputs Level 1 [Member] | Rabbi Trust Investments [Member]
Fixed income [Abstract]
Mutual funds	9		9
Rabbi trust investments subtotal	9	[10],[9]	9	[10],[9]
PECO Energy Co [Member] | Fair Value Inputs Level 2 [Member]
Fixed income [Abstract]
Deferred compensation	(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 [Abstract]
Mutual funds			0
PECO Energy Co [Member] | Fair Value Inputs Level 3 [Member] | Rabbi Trust Investments [Member]
Fixed income [Abstract]
Mutual funds			0
Baltimore Gas and Electric Company [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	53		31
Fixed income [Abstract]
Deferred compensation	(5)		(6)
Total assets	58		37
Total liabilities	(5)		(6)
Total net assets	53		31
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred compensation	5		6
Baltimore Gas and Electric Company [Member] | Rabbi Trust Investments [Member]
Fixed income [Abstract]
Mutual funds	5		6
Rabbi trust investments subtotal	5		6	[9]
Baltimore Gas and Electric Company [Member] | Fair Value Inputs Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash equivalents	53		31
Fixed income [Abstract]
Total assets	58		37
Total net assets	58		37
Baltimore Gas and Electric Company [Member] | Fair Value Inputs Level 1 [Member] | Rabbi Trust Investments [Member]
Fixed income [Abstract]
Mutual funds	5		6
Rabbi trust investments subtotal	5		6	[9]
Baltimore Gas and Electric Company [Member] | Fair Value Inputs Level 2 [Member]
Fixed income [Abstract]
Rabbi trust investments subtotal	0
Deferred compensation	(5)		(6)
Total assets	0
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 [Abstract]
Mutual funds	0
Rabbi trust investments subtotal	0
Baltimore Gas and Electric Company [Member] | Fair Value Inputs Level 3 [Member]
Fixed income [Abstract]
Rabbi trust investments subtotal	0
Total assets	0
Total net assets	0
Baltimore Gas and Electric Company [Member] | Fair Value Inputs Level 3 [Member] | Rabbi Trust Investments [Member]
Fixed income [Abstract]
Mutual funds	0
Rabbi trust investments subtotal	$ 0

[1] Excludes certain cash equivalents considered to be held-to-maturity and not reported at fair value.

[2] Excludes net assets (liabilities) of $14 million and $(5) million at June 30, 2014 and December 31, 2013, respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases.

[3] Excludes net assets of $7 million at both June 30, 2014 and December 31, 2013, respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases.

[4] The mutual funds held by the Rabbi trusts include $42 million related to deferred compensation and $1 million related to Supplemental Executive Retirement Plan at June 30, 2014, and $53 million related to deferred compensation and $1 million related to Supplemental Executive Retirement Plan at December 31, 2013.

[5] Excludes $34 million and $32 million of the cash surrender value of life insurance investments at June 30, 2014 and December 31, 2013, respectively.

[6] Includes collateral postings to counterparties. Collateral posted to counterparties, net of collateral paid to counterparties, totaled $49 million, $289 million and $152 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of June 30, 2014. Collateral posted (received) from counterparties, net of collateral paid to counterparties, totaled $6 million, $(124) million and $(26) million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2013.

[7] Excludes $10 million of the cash surrender value of life insurance investments at both June 30, 2014 and December 31, 2013.

[8] The Level 3 balance includes the current and noncurrent liability of $13 million and $121 million at June 30, 2014, respectively, and $17 million and $176 million at December 31, 2013, respectively, related to floating-to-fixed energy swap contracts with unaffiliated suppliers.

[9] Excludes $14 million of the cash surrender value of life insurance investments at both June 30, 2014 and December 31, 2013.

[10]