Fair Value of Financial Assets and Liabilities - Fair Value Measurements of Assets and Liabilities, Recurring and Nonrecurring (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	$ (360)	$ (403)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	1	3
Supplemental executive retirement plan fair value		1
Cash surrender value of life insurance investments excluded from Rabbi Trust investments	34	35
Derivative Liability, Noncurrent	(360)	(403)
Derivative Liability, Current	204	234
Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Rabbi Trust Investments [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred Compensation Plan Assets	45	45
Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		46
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		46
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	6,545	1,119
FinancialAssetsFairValueDisclosure1	18,913	14,081
Deferred Compensation Liability, Current and Noncurrent	(95)	(107)
Financial Liabilities Fair Value Disclosure	(659)	(744)
FinancialAssetLiabilitiesNetFairValueDisclosure1	18,254	13,337
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	6,545	1,119
Deferred Compensation Liability, Current and Noncurrent	(95)	(107)
Financial Liabilities Fair Value Disclosure	(659)	(744)
Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(543)	(524)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(543)	(524)
Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6,050)	(6,694)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6,050)	(6,694)
Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,770)	(6,702)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,770)	(6,702)
Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(113)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(113)
Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(103)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(103)
Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(41)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(41)
Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(23)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(23)
Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(54)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(54)
Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10,137	10,542
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10,137	10,542
Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,103	4,630
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,103	4,630
Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		7
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		7
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,076	2,262
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,076	2,262
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,701	5,242
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,701	5,242
Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,170	4,302
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,170	4,302
Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	368	245
Investments, Fair Value Disclosure		1
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	368	245
Investments, Fair Value Disclosure		1
Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Fair Value, Inputs, Level 1 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	353	434
Fair Value, Inputs, Level 1 [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Fair Value, Inputs, Level 1 [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		46
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		46
Fair Value, Inputs, Level 1 [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	6,545	1,119
FinancialAssetsFairValueDisclosure1	10,767	5,305
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	19	(9)
FinancialAssetLiabilitiesNetFairValueDisclosure1	10,786	5,296
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	6,545	1,119
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	19	(9)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(19)	(20)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(19)	(20)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,120)	(2,241)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,120)	(2,241)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(79)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(79)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,218)	(2,416)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,218)	(2,416)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(11)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(11)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(14)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(14)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(25)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(25)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,315	4,239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,315	4,239
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,274	2,423
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,274	2,423
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	6
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	6
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	11
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,872	3,035
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,872	3,035
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	46	47
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	46	47
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	301	208
Investments, Fair Value Disclosure		1
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	301	208
Investments, Fair Value Disclosure		1
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(155)	(114)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(6)	(1)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,625)	(1,667)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(85)	(201)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,865	1,982
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(14)	(18)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	8	17
Derivative Liability, Noncurrent		(195)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(195)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	2
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	2
Fair Value, Inputs, Level 2 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	435	800
Fair Value, Inputs, Level 2 [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(263)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(263)
Fair Value, Inputs, Level 2 [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	6
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	6
Fair Value, Inputs, Level 2 [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	57	89
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	57	89
Fair Value, Inputs, Level 2 [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7	8
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7	8
Fair Value, Inputs, Level 2 [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	10
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	10
Fair Value, Inputs, Level 2 [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	3
Fair Value, Inputs, Level 2 [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	75	110
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	75	110
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]
Investments, Fair Value Disclosure	236	316
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	236	316
Fair Value, Inputs, Level 2 [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Fair Value, Inputs, Level 2 [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	46	47
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	46	47
Fair Value, Inputs, Level 2 [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Fair Value, Inputs, Level 2 [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,856)	(2,029)
Fair Value, Inputs, Level 2 [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(21)	(13)
Fair Value, Inputs, Level 2 [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(61)	(23)
Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(37)	(31)
Fair Value, Inputs, Level 2 [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(6,330)	(6,813)
Fair Value, Inputs, Level 2 [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(263)	(512)
Fair Value, Inputs, Level 2 [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	4,737	5,296
Fair Value, Inputs, Level 2 [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(17)	(27)
Fair Value, Inputs, Level 2 [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	14	48
Derivative Liability, Noncurrent		(532)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(532)
Fair Value, Inputs, Level 2 [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	5
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
FinancialAssetsFairValueDisclosure1	5,809	6,747
Deferred Compensation Liability, Current and Noncurrent	(95)	(107)
Financial Liabilities Fair Value Disclosure	(262)	(427)
FinancialAssetLiabilitiesNetFairValueDisclosure1	5,547	6,320
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	(95)	(107)
Financial Liabilities Fair Value Disclosure	(262)	(427)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(146)	(196)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(146)	(196)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,478)	(3,458)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,478)	(3,458)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(140)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(140)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,472)	(3,557)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,472)	(3,557)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(124)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(124)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(103)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(103)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(41)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(41)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(9)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(9)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(29)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(29)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,008	5,612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,008	5,612
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	1
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	1
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,831	2,023
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,831	2,023
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	57	89
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	57	89
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2	3
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	10
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	10
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	3
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	70	105
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	70	105
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	82	121
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	82	121
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,783	3,067
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,783	3,067
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	67	37
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	67	37
Investments, Fair Value Disclosure		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(664)	(992)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(55)	(22)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(37)	(31)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(2,561)	(3,465)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(140)	(284)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	2,037	2,757
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(3)	(9)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	6	31
Derivative Liability, Noncurrent		(295)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(295)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	245	172
Fair Value, Inputs, Level 3 [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
FinancialAssetsFairValueDisclosure1	2,337	2,029
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(416)	(308)
FinancialAssetLiabilitiesNetFairValueDisclosure1	1,921	1,721
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(416)	(308)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(416)	(308)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(416)	(308)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,452)	(995)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,452)	(995)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(44)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(44)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,080)	(729)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,080)	(729)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	814	691
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	814	691
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Investments, Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,347)	(1,151)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(2,144)	(1,681)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(38)	(27)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	835	557
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Derivative Liability, Noncurrent		(42)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(42)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	3
Exelon Generation Co L L C [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(139)	(105)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash surrender value of life insurance investments excluded from Rabbi Trust investments	12	11
Derivative Liability, Noncurrent	(139)	(105)
Derivative Liability, Current	182	214
Exelon Generation Co L L C [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Exelon Generation Co L L C [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	225	405
FinancialAssetsFairValueDisclosure1	12,526	13,329
Deferred Compensation Liability, Current and Noncurrent	(29)	(31)
Financial Liabilities Fair Value Disclosure	(350)	(350)
FinancialAssetLiabilitiesNetFairValueDisclosure1	12,176	12,979
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	225	405
Deferred Compensation Liability, Current and Noncurrent	(29)	(31)
Financial Liabilities Fair Value Disclosure	(350)	(350)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(300)	(317)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(300)	(317)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,807)	(6,487)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,807)	(6,487)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,770)	(6,702)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,770)	(6,702)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(2)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(2)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(2)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(2)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(12)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(12)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(23)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(23)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(35)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(35)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10,137	10,542
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10,137	10,542
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,103	4,630
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,103	4,630
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		7
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		7
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,076	2,262
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,076	2,262
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,701	5,242
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,701	5,242
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,170	4,302
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,170	4,302
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	368	245
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	368	245
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	225	405
FinancialAssetsFairValueDisclosure1	4,417	4,558
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	19	(9)
FinancialAssetLiabilitiesNetFairValueDisclosure1	4,436	4,549
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	225	405
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	19	(9)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(19)	(20)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(19)	(20)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,120)	(2,241)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,120)	(2,241)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(79)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(79)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,218)	(2,416)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,218)	(2,416)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(11)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(11)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(14)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(14)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(25)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(25)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,315	4,239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,315	4,239
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,274	2,423
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,274	2,423
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	6
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	6
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	11
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,872	3,035
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,872	3,035
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	16	16
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	16	16
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	301	208
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	301	208
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(155)	(114)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(6)	(1)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,625)	(1,667)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(85)	(201)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,865	1,982
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(14)	(18)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	8	17
Derivative Liability, Noncurrent		(195)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(195)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(263)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(263)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
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]
Investments, Fair Value Disclosure	16	16
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	16	16
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,856)	(2,029)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(21)	(12)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(24)	(18)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	(8)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(6,330)	(6,813)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(263)	(512)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	4,737	5,296
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(17)	(27)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	14	29
Derivative Liability, Noncurrent		(532)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(532)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	3
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
FinancialAssetsFairValueDisclosure1	5,772	6,742
Deferred Compensation Liability, Current and Noncurrent	(29)	(31)
Financial Liabilities Fair Value Disclosure	(196)	(240)
FinancialAssetLiabilitiesNetFairValueDisclosure1	5,576	6,502
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	(29)	(31)
Financial Liabilities Fair Value Disclosure	(196)	(240)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(146)	(196)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(146)	(196)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,478)	(3,458)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,478)	(3,458)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(140)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(140)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,472)	(3,557)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,472)	(3,557)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(13)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(13)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(2)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(2)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(12)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(12)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(9)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(9)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(10)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(10)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,008	5,612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,008	5,612
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	1
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	1
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,831	2,023
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,831	2,023
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	57	89
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	57	89
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2	3
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	10
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	10
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	3
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	70	105
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	70	105
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	82	121
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	82	121
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,783	3,067
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,783	3,067
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	67	37
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	67	37
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(664)	(992)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(18)	(17)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	(8)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(2,561)	(3,465)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(140)	(284)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	2,037	2,757
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(3)	(9)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	6	12
Derivative Liability, Noncurrent		(295)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(295)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
FinancialAssetsFairValueDisclosure1	2,337	2,029
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(173)	(101)
FinancialAssetLiabilitiesNetFairValueDisclosure1	2,164	1,928
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(173)	(101)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(173)	(101)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(173)	(101)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,209)	(788)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,209)	(788)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(44)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(44)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,080)	(729)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,080)	(729)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	814	691
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	814	691
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,347)	(1,151)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(2,144)	(1,681)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(38)	(27)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	835	557
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Derivative Liability, Noncurrent		(42)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(42)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	3
PECO Energy Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	4	12
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash surrender value of life insurance investments excluded from Rabbi Trust investments	12	14
Cash and Cash Equivalents, Fair Value Disclosure	4	12
PECO Energy Co [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	8	9
FinancialAssetsFairValueDisclosure1	12	21
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(11)	(15)
Financial Liabilities Fair Value Disclosure	(11)	(15)
FinancialAssetLiabilitiesNetFairValueDisclosure1	1	6
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Investments, Fair Value Disclosure	8	9
Deferred Compensation Liability, Current and Noncurrent	(11)	(15)
Financial Liabilities Fair Value Disclosure	(11)	(15)
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	4	12
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	4	12
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	8	9
FinancialAssetsFairValueDisclosure1	12	21
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	12	21
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Investments, Fair Value Disclosure	8	9
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	0
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(11)	(15)
Financial Liabilities Fair Value Disclosure	(11)	(15)
FinancialAssetLiabilitiesNetFairValueDisclosure1	(11)	(15)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(11)	(15)
Financial Liabilities Fair Value Disclosure	(11)	(15)
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	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 and Cash Equivalents, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	0
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	25
Derivative Liability, Noncurrent	(221)	(187)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(221)	(187)
Derivative Liability, Current	22	20
Cash and Cash Equivalents, Fair Value Disclosure	0	25
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	25
Derivative Liability, Noncurrent	(243)	(207)
Deferred Compensation Liability, Current and Noncurrent	(7)	(8)
Financial Liabilities Fair Value Disclosure	(250)	(215)
FinancialAssetLiabilitiesNetFairValueDisclosure1	(250)	(190)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(243)	(207)
Deferred Compensation Liability, Current and Noncurrent	(7)	(8)
Financial Liabilities Fair Value Disclosure	(250)	(215)
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	25
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	25
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	25
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	0	25
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	0
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(7)	(8)
Financial Liabilities Fair Value Disclosure	(7)	(8)
FinancialAssetLiabilitiesNetFairValueDisclosure1	(7)	(8)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(7)	(8)
Financial Liabilities Fair Value Disclosure	(7)	(8)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	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 and Cash Equivalents, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	0
Derivative Liability, Noncurrent	(243)	(207)
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(243)	(207)
FinancialAssetLiabilitiesNetFairValueDisclosure1	(243)	(207)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(243)	(207)
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(243)	(207)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	68	103
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	68	103
Baltimore Gas and Electric Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
FinancialAssetsFairValueDisclosure1	73	108
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(4)	(5)
Financial Liabilities Fair Value Disclosure	(4)	(5)
FinancialAssetLiabilitiesNetFairValueDisclosure1	69	103
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Investments, Fair Value Disclosure	5	5
Deferred Compensation Liability, Current and Noncurrent	(4)	(5)
Financial Liabilities Fair Value Disclosure	(4)	(5)
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 and Cash Equivalents, Fair Value Disclosure	68	103
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	68	103
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
FinancialAssetsFairValueDisclosure1	73	108
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	73	108
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Investments, Fair Value Disclosure	5	5
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
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 and Cash Equivalents, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	0
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(4)	(5)
Financial Liabilities Fair Value Disclosure	(4)	(5)
FinancialAssetLiabilitiesNetFairValueDisclosure1	(4)	(5)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(4)	(5)
Financial Liabilities Fair Value Disclosure	(4)	(5)
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	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 and Cash Equivalents, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	0
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Nuclear Decommissioning [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	$ (34)	$ (5)