Fair Value of Financial Assets and Liabilities - Fair Value Measurement of Assets and Liabilities, Recurring and Nonrecurring (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 1,119	[1]	$ 1,230	[1]
Rabbi trust investments subtotal				[2]
Other investments	5		15
Total assets	14,081		11,162
Deferred compensation obligation	(107)		(114)
Total liabilities	(744)		(573)
Total net assets	13,337		10,589
Cash surrender value of life insurance investments excluded from Rabbi Trust investments			35
Mark-to-market derivative liabilities (noncurrent liabilities)	403		300
Mark-to-market derivative liabilities (current liabilities)	234		159
Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	31
Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(41)
Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	13
Mark-to-market derivative liabilities (noncurrent liabilities)	289		285
Mark-to-market derivative liabilities (current liabilities)	235		158
Derivative [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(103)
Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	27
Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(23)
Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	245		459
Equity	4,630		3,913
Foreign	612		249
Equity funds subtotal	5,242		4,162
Corporate debt securities	2,262		1,784
U.S. Treasury and agencies	996		882
Foreign governments	95		87
State and municipal debt	438		294
Other	511		75
Fixed income subtotal	4,302		3,122
Middle market lending	366		314
Private equity	83		5
Real estate	3
Other	301		14
Nuclear decommissioning trust fund investments subtotal	10,542	[3]	8,076	[3]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	(5)
Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	15		26
Equity	7		16
Corporate debt securities	89		227
U.S. Treasury and agencies	8		49
State and municipal debt	10		20
Other	3
Fixed income subtotal	110		296
Middle market lending	184		112
Other			1
Pledged assets for Zion Station decommissioning subtotal	316	[4]	451	[4]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	3		7
Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1	[2]	2	[2]
Mutual funds	46	[2],[5]	54	[2],[5]
Rabbi trust investments subtotal	47	[2]	56	[2]
Deferred compensation obligation	(45)		(53)
Supplemental executive retirement plan fair value	1		1
Cash surrender value of life insurance investments excluded from Rabbi Trust investments	11		32
Commodity Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	6,813		3,960
Proprietary trading	512		1,761
Effect of netting and allocation of collateral received/(paid)	5,296	[6]	4,424	[6]
Commodity derivative subtotal	2,029		1,297
Interest Rate Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	(48)		(32)
Interest rate and foreign currency derivative			(69)
Interest rate and foreign currency derivatives subtotal	(23)		(37)
Commodity Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	(6,694)		(3,020)
Proprietary trading	(532)		(1,703)
Effect of netting and allocation of collateral received/(paid)	(6,702)	[6]	(4,280)	[6]
Commodity derivative subtotal	(524)		(443)
Interest Rate Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	(54)		(32)
Interest rate and foreign currency derivative	0		(48)
Interest rate and foreign currency derivatives subtotal	(113)		(16)
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1,119	[1]	1,230	[1]
Other investments	2		0
Total assets	5,305		4,533
Deferred compensation obligation	0		0
Total liabilities	(9)		1
Total net assets	5,296		4,534
Collateral received from counterparties, net of collateral paid to counterparties	434		6
Fair Value, Inputs, Level 1 [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Fair Value, Inputs, Level 1 [Member] | Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0
Fair Value, Inputs, Level 1 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Fair Value, Inputs, Level 1 [Member] | Derivative [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0
Fair Value, Inputs, Level 1 [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	18
Fair Value, Inputs, Level 1 [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(14)
Fair Value, Inputs, Level 1 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	208		459
Equity	2,423		1,642
Foreign	612		249
Equity funds subtotal	3,035		1,891
Corporate debt securities	0		0
U.S. Treasury and agencies	996		882
Foreign governments	0		0
State and municipal debt	0		0
Other	0		0
Fixed income subtotal	996		882
Middle market lending	0		0
Private equity	0		0
Real estate	0
Other	0		0
Nuclear decommissioning trust fund investments subtotal	4,239	[3]	3,232	[3]
Fair Value, Inputs, Level 1 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0		0
Equity	6		16
Corporate debt securities	0		0
U.S. Treasury and agencies	5		45
State and municipal debt	0		0
Other	0
Fixed income subtotal	5		45
Middle market lending	0		0
Other			0
Pledged assets for Zion Station decommissioning subtotal	11	[4]	61	[4]
Fair Value, Inputs, Level 1 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1	[2]	2	[2]
Mutual funds	46	[2],[5]	54	[2],[5]
Rabbi trust investments subtotal	47	[2]	56	[2]
Fair Value, Inputs, Level 1 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	1,667		493
Proprietary trading	201		324
Effect of netting and allocation of collateral received/(paid)	1,982	[6]	863	[6]
Commodity derivative subtotal	(114)		(46)
Fair Value, Inputs, Level 1 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	(17)		(30)
Interest rate and foreign currency derivative			(30)
Interest rate and foreign currency derivatives subtotal	(1)		0
Fair Value, Inputs, Level 1 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	(2,241)		(540)
Proprietary trading	(195)		(328)
Effect of netting and allocation of collateral received/(paid)	(2,416)	[6]	(869)	[6]
Commodity derivative subtotal	(20)		1
Fair Value, Inputs, Level 1 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	(25)		(31)
Interest rate and foreign currency derivative	0		(31)
Interest rate and foreign currency derivatives subtotal	11		0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	[1]	0	[1]
Other investments	0		0
Total assets	6,747		5,575
Deferred compensation obligation	(107)		(114)
Total liabilities	(427)		(269)
Total net assets	6,320		5,306
Collateral received from counterparties, net of collateral paid to counterparties	800		(124)
Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	31
Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(41)
Fair Value, Inputs, Level 2 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	13
Fair Value, Inputs, Level 2 [Member] | Derivative [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(103)
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	9
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(9)
Fair Value, Inputs, Level 2 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	37		0
Equity	2,207		2,271
Foreign	0		0
Equity funds subtotal	2,207		2,271
Corporate debt securities	2,023		1,753
U.S. Treasury and agencies	0		0
Foreign governments	95		87
State and municipal debt	438		294
Other	511		75
Fixed income subtotal	3,067		2,209
Middle market lending	0		0
Private equity	0		0
Real estate	0
Other	301		14
Nuclear decommissioning trust fund investments subtotal	5,612	[3]	4,494	[3]
Fair Value, Inputs, Level 2 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	15		26
Equity	1		0
Corporate debt securities	89		227
U.S. Treasury and agencies	3		4
State and municipal debt	10		20
Other	3
Fixed income subtotal	105		251
Middle market lending	0		0
Other			1
Pledged assets for Zion Station decommissioning subtotal	121	[4]	278	[4]
Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	[2]	0	[2]
Mutual funds	0	[2],[5]	0	[2],[5]
Rabbi trust investments subtotal	0	[2]	0	[2]
Fair Value, Inputs, Level 2 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	3,465		2,582
Proprietary trading	284		1,315
Effect of netting and allocation of collateral received/(paid)	2,757	[6]	3,131	[6]
Commodity derivative subtotal	992		766
Fair Value, Inputs, Level 2 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	(31)		(2)
Interest rate and foreign currency derivative			(39)
Interest rate and foreign currency derivatives subtotal	(22)		(37)
Fair Value, Inputs, Level 2 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	(3,458)		(1,890)
Proprietary trading	(295)		(1,256)
Effect of netting and allocation of collateral received/(paid)	(3,557)	[6]	(3,007)	[6]
Commodity derivative subtotal	(196)		(139)
Fair Value, Inputs, Level 2 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	(29)		(1)
Interest rate and foreign currency derivative	0		(17)
Interest rate and foreign currency derivatives subtotal	(124)		(16)
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	[1]	0	[1]
Other investments	3		15
Total assets	2,029		1,054
Deferred compensation obligation	0		0
Total liabilities	(308)		(305)
Total net assets	1,721		749
Collateral received from counterparties, net of collateral paid to counterparties	172		(26)
Mark-to-market derivative liabilities (noncurrent liabilities)			176
Fair Value, Inputs, Level 3 [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Fair Value, Inputs, Level 3 [Member] | Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0
Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0
Fair Value, Inputs, Level 3 [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Fair Value, Inputs, Level 3 [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0
Fair Value, Inputs, Level 3 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0		0
Equity	0		0
Foreign	0		0
Equity funds subtotal	0		0
Corporate debt securities	239		31
U.S. Treasury and agencies	0		0
Foreign governments	0		0
State and municipal debt	0		0
Other	0		0
Fixed income subtotal	239		31
Middle market lending	366		314
Private equity	83		5
Real estate	3
Other	0		0
Nuclear decommissioning trust fund investments subtotal	691	[3]	350	[3]
Fair Value, Inputs, Level 3 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0		0
Equity	0		0
Corporate debt securities	0		0
U.S. Treasury and agencies	0		0
State and municipal debt	0		0
Other	0
Fixed income subtotal	0		0
Middle market lending	184		112
Other			0
Pledged assets for Zion Station decommissioning subtotal	184	[4]	112	[4]
Fair Value, Inputs, Level 3 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	[2]	0	[2]
Mutual funds	0	[2],[5]	0	[2],[5]
Rabbi trust investments subtotal	0	[2]	0	[2]
Fair Value, Inputs, Level 3 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	1,681		885
Proprietary trading	27		122
Effect of netting and allocation of collateral received/(paid)	557	[6]	430	[6]
Commodity derivative subtotal	1,151		577
Fair Value, Inputs, Level 3 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	0		0
Interest rate and foreign currency derivative			0
Interest rate and foreign currency derivatives subtotal	0		0
Fair Value, Inputs, Level 3 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	(995)		(590)
Proprietary trading	(42)		(119)
Effect of netting and allocation of collateral received/(paid)	(729)	[6]	(404)	[6]
Commodity derivative subtotal	(308)		(305)
Fair Value, Inputs, Level 3 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	0		0
Interest rate and foreign currency derivative	0		0
Interest rate and foreign currency derivatives subtotal	0		0
Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	405	[1]	1,006	[1]
Other investments	3		15
Total assets	13,329		10,888
Derivative liabilities	(293)	[7]	(210)	[7]
Deferred compensation obligation	(31)		(29)
Total liabilities	(350)		(291)
Total net assets	12,979		10,597
Mark-to-market derivative liabilities (noncurrent liabilities)	105		120
Mark-to-market derivative liabilities (current liabilities)	214		142
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	8
Mark-to-market derivative liabilities (noncurrent liabilities)	1,540		804
Mark-to-market derivative liabilities (current liabilities)	4,947		2,023
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(12)
Exelon Generation Co L L C [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	12
Mark-to-market derivative liabilities (noncurrent liabilities)	102	[8]	109	[9]
Mark-to-market derivative liabilities (current liabilities)	215	[8]	141	[9]
Exelon Generation Co L L C [Member] | Derivative [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(2)
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	27
Mark-to-market derivative liabilities (current liabilities)	2
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(23)
Exelon Generation Co L L C [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	245		459
Equity	4,630		3,913
Foreign	612		249
Equity funds subtotal	5,242		4,162
Corporate debt securities	2,262		1,784
U.S. Treasury and agencies	996		882
Foreign governments	95		87
State and municipal debt	438		294
Other	511		75
Fixed income subtotal	4,302		3,122
Middle market lending	366		314
Private equity	83		5
Real estate	3
Other	301		14
Nuclear decommissioning trust fund investments subtotal	10,542	[3]	8,076	[3]
Exelon Generation Co L L C [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	15		26
Equity	7		16
Corporate debt securities	89		227
U.S. Treasury and agencies	8		49
State and municipal debt	10		20
Other	3
Fixed income subtotal	110		296
Middle market lending	184		112
Other			1
Pledged assets for Zion Station decommissioning subtotal	316	[4]	451	[4]
Exelon Generation Co L L C [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	[2]	0	[2]
Mutual funds	16	[2],[5]	13	[2],[5]
Rabbi trust investments subtotal	16	[2]	13	[2]
Cash surrender value of life insurance investments excluded from Rabbi Trust investments			10
Exelon Generation Co L L C [Member] | Commodity Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	6,813		3,960
Proprietary trading	512		1,761
Effect of netting and allocation of collateral received/(paid)	5,296	[6]	4,424	[6]
Commodity derivative subtotal	2,029		1,297
Exelon Generation Co L L C [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	(29)		(32)
Interest rate and foreign currency derivative			(62)
Interest rate and foreign currency derivatives subtotal	(18)		(30)
Exelon Generation Co L L C [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	(6,487)		(2,827)
Proprietary trading	(532)		(1,703)
Effect of netting and allocation of collateral received/(paid)	(6,702)	[6]	(4,280)	[6]
Commodity derivative subtotal	(317)		(250)
Exelon Generation Co L L C [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	(35)		(32)
Interest rate and foreign currency derivative	0		(44)
Interest rate and foreign currency derivatives subtotal	(2)		(12)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	405	[1]	1,006	[1]
Other investments	0		0
Total assets	4,558		4,266
Deferred compensation obligation	0		0
Total liabilities	(9)		1
Total net assets	4,549		4,267
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	18
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(14)
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 and Nonrecurring Basis [Line Items]
Cash equivalents	208		459
Equity	2,423		1,642
Foreign	612		249
Equity funds subtotal	3,035		1,891
Corporate debt securities	0		0
U.S. Treasury and agencies	996		882
Foreign governments	0		0
State and municipal debt	0		0
Other	0		0
Fixed income subtotal	996		882
Middle market lending	0		0
Private equity	0		0
Real estate	0
Other	0		0
Nuclear decommissioning trust fund investments subtotal	4,239	[3]	3,232	[3]
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0		0
Equity	6		16
Corporate debt securities	0		0
U.S. Treasury and agencies	5		45
State and municipal debt	0		0
Other	0
Fixed income subtotal	5		45
Middle market lending	0		0
Other			0
Pledged assets for Zion Station decommissioning subtotal	11	[4]	61	[4]
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 and Nonrecurring Basis [Line Items]
Cash equivalents	0	[2]	0	[2]
Mutual funds	16	[2],[5]	13	[2],[5]
Rabbi trust investments subtotal	16	[2]	13	[2]
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	1,667		493
Proprietary trading	201		324
Effect of netting and allocation of collateral received/(paid)	1,982	[6]	863	[6]
Commodity derivative subtotal	(114)		(46)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	(17)		(30)
Interest rate and foreign currency derivative			(30)
Interest rate and foreign currency derivatives subtotal	(1)		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	(2,241)		(540)
Proprietary trading	(195)		(328)
Effect of netting and allocation of collateral received/(paid)	(2,416)	[6]	(869)	[6]
Commodity derivative subtotal	(20)		1
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	(25)		(31)
Interest rate and foreign currency derivative	0		(31)
Interest rate and foreign currency derivatives subtotal	11		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	[1]	0	[1]
Other investments	0		0
Total assets	6,742		5,568
Deferred compensation obligation	(31)		(29)
Total liabilities	(240)		(180)
Total net assets	6,502		5,388
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	8
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(12)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	12
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(2)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	9
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(9)
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 and Nonrecurring Basis [Line Items]
Cash equivalents	37		0
Equity	2,207		2,271
Foreign	0		0
Equity funds subtotal	2,207		2,271
Corporate debt securities	2,023		1,753
U.S. Treasury and agencies	0		0
Foreign governments	95		87
State and municipal debt	438		294
Other	511		75
Fixed income subtotal	3,067		2,209
Middle market lending	0		0
Private equity	0		0
Real estate	0
Other	301		14
Nuclear decommissioning trust fund investments subtotal	5,612	[3]	4,494	[3]
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 and Nonrecurring Basis [Line Items]
Cash equivalents	15		26
Equity	1		0
Corporate debt securities	89		227
U.S. Treasury and agencies	3		4
State and municipal debt	10		20
Other	3
Fixed income subtotal	105		251
Middle market lending	0		0
Other			1
Pledged assets for Zion Station decommissioning subtotal	121	[4]	278	[4]
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	[2]	0	[2]
Mutual funds	0	[2],[5]	0	[2],[5]
Rabbi trust investments subtotal	0	[2]	0	[2]
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	3,465		2,582
Proprietary trading	284		1,315
Effect of netting and allocation of collateral received/(paid)	2,757	[6]	3,131	[6]
Commodity derivative subtotal	992		766
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	(12)		(2)
Interest rate and foreign currency derivative			(32)
Interest rate and foreign currency derivatives subtotal	(17)		(30)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	(3,458)		(1,890)
Proprietary trading	(295)		(1,256)
Effect of netting and allocation of collateral received/(paid)	(3,557)	[6]	(3,007)	[6]
Commodity derivative subtotal	(196)		(139)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	(10)		(1)
Interest rate and foreign currency derivative	0		(13)
Interest rate and foreign currency derivatives subtotal	(13)		(12)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	[1]	0	[1]
Other investments	3		15
Total assets	2,029		1,054
Deferred compensation obligation	0		0
Total liabilities	(101)		(112)
Total net assets	1,928		942
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0		0
Equity	0		0
Foreign	0		0
Equity funds subtotal	0		0
Corporate debt securities	239		31
U.S. Treasury and agencies	0		0
Foreign governments	0		0
State and municipal debt	0		0
Other	0		0
Fixed income subtotal	239		31
Middle market lending	366		314
Private equity	83		5
Real estate	3
Other	0		0
Nuclear decommissioning trust fund investments subtotal	691	[3]	350	[3]
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0		0
Equity	0		0
Corporate debt securities	0		0
U.S. Treasury and agencies	0		0
State and municipal debt	0		0
Other	0
Fixed income subtotal	0		0
Middle market lending	184		112
Other			0
Pledged assets for Zion Station decommissioning subtotal	184	[4]	112	[4]
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	[2]	0	[2]
Mutual funds	0	[2],[5]	0	[2],[5]
Rabbi trust investments subtotal	0	[2]	0	[2]
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Commodity Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	1,681		885
Proprietary trading	27		122
Effect of netting and allocation of collateral received/(paid)	557	[6]	430	[6]
Commodity derivative subtotal	1,151		577
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Interest Rate Mark To Market Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	0		0
Interest rate and foreign currency derivative			0
Interest rate and foreign currency derivatives subtotal	0		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Commodity Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Economic hedges	(788)		(397)
Proprietary trading	(42)		(119)
Effect of netting and allocation of collateral received/(paid)	(729)	[6]	(404)	[6]
Commodity derivative subtotal	(101)		(112)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Interest Rate Mark To Market Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect of netting and allocation of collateral received/(paid)	0		0
Interest rate and foreign currency derivative	0		0
Interest rate and foreign currency derivatives subtotal	0		0
Commonwealth Edison Co [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	25		0
Commodity derivative subtotal	(207)	[10]	(193)	[10]
Total assets	25		5
Deferred compensation obligation	(8)		(8)
Total liabilities	(215)		(201)
Total net assets	(190)		(196)
Mark-to-market derivative liabilities (noncurrent liabilities)	187		176
Mark-to-market derivative liabilities (current liabilities)	20		17
Commonwealth Edison Co [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mark-to-market derivative liabilities (noncurrent liabilities)	187	[11]	176	[11]
Mark-to-market derivative liabilities (current liabilities)	20	[11]	17	[11]
Commonwealth Edison Co [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	0	[12]	5	[12]
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	25		0
Commodity derivative subtotal	0	[10]	0	[10]
Total assets	25		5
Deferred compensation obligation	0		0
Total liabilities	0		0
Total net assets	25		5
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	0	[12]	5	[12]
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0		0
Commodity derivative subtotal	0	[10]	0	[10]
Total assets	0		0
Deferred compensation obligation	(8)		(8)
Total liabilities	(8)		(8)
Total net assets	(8)		(8)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	0	[12]	0	[12]
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0		0
Commodity derivative subtotal	(207)	[10]	(193)	[10]
Total assets	0		0
Deferred compensation obligation	0		0
Total liabilities	(207)		(193)
Total net assets	(207)		(193)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	0	[12]	0	[12]
PECO Energy Co [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	12		175
Commodity derivative subtotal	0	[10]	0	[10]
Total assets	21		184
Deferred compensation obligation	(15)		(17)
Total liabilities	(15)		(17)
Total net assets	6		167
Mark-to-market derivative liabilities (noncurrent liabilities)	14
PECO Energy Co [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	9	[12]	9	[12]
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	12		175
Commodity derivative subtotal	0	[10]	0	[10]
Total assets	21		184
Deferred compensation obligation	0		0
Total liabilities	0		0
Total net assets	21		184
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	9	[12]	9	[12]
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0		0
Commodity derivative subtotal	0	[10]	0	[10]
Total assets	0		0
Deferred compensation obligation	(15)		(17)
Total liabilities	(15)		(17)
Total net assets	(15)		(17)
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	0	[12]	0	[12]
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0		0
Commodity derivative subtotal	0	[10]	0	[10]
Total assets	0		0
Deferred compensation obligation	0		0
Total liabilities	0		0
Total net assets	0		0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	0	[12]	0	[12]
Baltimore Gas and Electric Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	103		31
Commodity derivative subtotal	0	[10]	0	[10]
Total assets	108		37
Deferred compensation obligation	(5)		(6)
Total liabilities	(5)		(6)
Total net assets	103		31
Baltimore Gas and Electric Company [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	5	[12]	6	[12]
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	103		31
Commodity derivative subtotal	0	[10]	0	[10]
Total assets	108		37
Deferred compensation obligation	0		0
Total liabilities	0		0
Total net assets	108		37
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	5	[12]	6	[12]
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0		0
Commodity derivative subtotal	0	[10]	0	[10]
Total assets	0		0
Deferred compensation obligation	(5)		(6)
Total liabilities	(5)		(6)
Total net assets	(5)		(6)
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	0	[12]	0	[12]
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0		0
Commodity derivative subtotal	0	[10]	0	[10]
Total assets	0		0
Deferred compensation obligation	0		0
Total liabilities	0		0
Total net assets	0		0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	$ 0	[12]	$ 0	[12]

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

[2] The mutual funds held by the Rabbi trusts at Exelon Consolidated include $45 million related to deferred compensation and $1 million related to a Supplemental Executive Retirement Plan at December 31, 2014, and $53 million related to deferred compensation and $1 million related to a Supplemental Executive Retirement Plan at December 31, 2013.

[3] Excludes net liabilities of $5 million at both December 31, 2014 and 2013. These items consist of receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases.

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

[5] Excludes $35 million and $32 million of cash surrender value of life insurance investment at December 31, 2014 and 2013, respectively, at Exelon Consolidated. Excludes $11 million and $10 million of cash surrender value of life insurance investment at December 31, 2014 and 2013, respectively, at Generation.

[6] Includes collateral postings (received) to/from counterparties. Collateral posted (received) to/from counterparties, net of collateral paid to counterparties, totaled $434 million, $800 million and $172 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2014. Collateral posted (received) to/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] (c)Amount represents the net fair value of out-of-the-money derivative contracts containing credit-risk related contingent features after considering the mitigating effects of offsetting positions under master netting arrangements and reflects the actual net liability upon which any potential contingent collateral obligations would be based.

[8] Current and noncurrent assets are shown net of collateral of $(416) million and $(171) million, respectively, and current and noncurrent liabilities are shown net of collateral of $(599) million and $(220) million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $1,406 million at December 31, 2014.

[9] Current and noncurrent assets are shown net of collateral of $84 million and $72 million, respectively. Current liabilities are shown net of collateral of $(12) million. Collateral related to noncurrent liabilities was $0 million. 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.

[10] The Level 3 balance includes the current and noncurrent liability of $20 million and $187 million, respectively, at December 31, 2014, and $17 million and $176 million, respectively, at December 31, 2013, related to floating-to-fixed energy swap contracts with unaffiliated suppliers.

[11] Includes current and noncurrent liabilities relating to floating-to-fixed energy swap contracts with unaffiliated suppliers.

[12] At PECO, excludes $14 million of the cash surrender value of life insurance investments at both December 31, 2014 and 2013