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Fair Value of Financial Assets and Liabilities - Fair Value Measurements of Assets and Liabilities, Recurring and Nonrecurring (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
Derivative Asset, Notional Amount $ 1,155   $ 1,236
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     5,766
U.S. Treasury and agencies      
Fixed income subtotal 223    
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (408)   (374)
Derivative Liability, Current 203   205
Derivative, Collateral, Right to Reclaim Cash 38   52
Derivative Asset, Notional Amount 1,155   1,236
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value 11   8
Nuclear Decommissioning Trust Fund Investments [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments (17)   (3)
Cash Equivalents NDT [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 277    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 277    
Corporate Debt Securities [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 2,111    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 2,111    
Private Equity Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 5,170    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 5,170    
Pledged Assets For Zion Station Decommissioning [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments 0   1
Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 14    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 14    
Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 46   48
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 46   48
6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 80   36
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 80   36
Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 13,732   18,556
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 721   2
Deferred Compensation Liability, Current and Noncurrent (131)   (99)
Financial Liabilities Fair Value Disclosure (742)   (678)
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 12,990   17,878
Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (585)   (563)
Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (7,892)   (6,827)
Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (26)   (16)
Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (7,451)   (6,391)
Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (23)   (16)
Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (8)   (3)
Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (11)   (12)
Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (16)   (15)
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 285   326
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 285   326
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 10,543   10,345
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 10,543   10,345
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 2,611   2,660
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 1,415   1,338
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 1,415   1,338
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     2,066
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     2,066
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 45   61
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 45   61
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 130   125
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 130   125
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 130    
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 40   35
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 40   35
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 40    
Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 85   105
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     4,902
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     4,902
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 4,296   4,328
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 4,296   4,328
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 376   390
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 440   428
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 440   428
Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     311
Investments, Fair Value Disclosure 83    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 83    
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 440   537
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 440   537
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 376    
Fair Value, Measurements, Recurring [Member] | Other [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 190   216
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 190   216
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 190    
Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 35   17
Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 85    
Fair Value, Inputs, Level 1 [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     5,766
U.S. Treasury and agencies      
Fixed income subtotal 129    
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Collateral received from counterparties, net of collateral paid to counterparties 350   476
Fair Value, Inputs, Level 1 [Member] | Economic hedge Interest and Currency [Member]      
Equities      
Derivative Asset 0   0
Fair Value, Inputs, Level 1 [Member] | Cash Equivalents NDT [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 266    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 266    
Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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 3,273    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 3,273    
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 1,875    
Fair Value, Inputs, Level 1 [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Fair Value, Inputs, Level 1 [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 46   48
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 46   48
Fair Value, Inputs, Level 1 [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 5,720   10,372
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 721    
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 8   25
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 5,728   10,397
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (8)   (25)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (2,054)   (2,382)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (28)   (33)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (2,090)   (2,440)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (11)   (12)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (11)   (12)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]      
Equities      
Derivative Asset 117   6
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 4,941   4,550
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 4,941   4,550
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 1,402   1,323
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 1,402   1,323
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     125
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     35
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 39   7
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 39   7
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     3,008
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     3,008
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     1,894
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 1,402   1,323
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 1,402   1,323
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 equivalents     219
Investments, Fair Value Disclosure 83    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 83    
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]      
Equities      
Derivative Asset 0   0
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]      
Equities      
Derivative Asset 31   36
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of netting and allocation of collateral [Member]      
Equities      
Derivative Asset (1,739)   (1,964)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest rate and foreign currency derivative assets [Member]      
Equities      
Derivative Asset 7   7
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     390
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     216
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 equivalents 35   0
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 1   1
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 1   1
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 3   6
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 3   6
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     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 3   6
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 3   6
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     105
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]      
Equities      
Derivative Asset 1,591   1,922
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]      
Equities      
Derivative Asset 11   10
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effectsofnettingandallocationofcollateral1 [Member]      
Equities      
Derivative Asset (4)   (3)
Fair Value, Inputs, Level 2 [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     0
U.S. Treasury and agencies      
Fixed income subtotal 74    
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Collateral received from counterparties, net of collateral paid to counterparties 538   557
Fair Value, Inputs, Level 2 [Member] | Proprietary Trading Liabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (144)   (127)
Fair Value, Inputs, Level 2 [Member] | Economic hedge Interest and Currency [Member]      
Equities      
Derivative Asset 20   20
Fair Value, Inputs, Level 2 [Member] | Commodity Derivative Assets [Member]      
Equities      
Derivative Asset 1,960   2,069
Fair Value, Inputs, Level 2 [Member] | Cash Equivalents NDT [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 11    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 11    
Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 1,868    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 1,868    
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 21    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 21    
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 183   205
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 183   205
Fair Value, Inputs, Level 2 [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 14    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 14    
Fair Value, Inputs, Level 2 [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Fair Value, Inputs, Level 2 [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 60   36
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 60   36
Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member]      
Equities      
Derivative Asset 42   25
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 36   33
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 36   33
Fair Value, Inputs, Level 2 [Member] | Proprietary Trading [Member]      
Equities      
Derivative Asset 143   130
Fair Value, Inputs, Level 2 [Member] | Effects of netting and allocation of collateral [Member]      
Equities      
Derivative Asset (6,411)   (5,157)
Fair Value, Inputs, Level 2 [Member] | Interest rate and foreign currency derivative assets [Member]      
Equities      
Derivative Asset 66   54
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 8   6
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 8   6
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 5   8
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 5   8
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 25   46
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 25   46
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     1
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 30   55
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 30   55
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 110   127
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 110   127
Fair Value, Inputs, Level 2 [Member] | Economic Hedging Instrument [Member]      
Equities      
Derivative Asset 8,228   7,096
Fair Value, Inputs, Level 2 [Member] | Proprietary Trading Interest and Currency Derivative [Member]      
Equities      
Derivative Asset 13   15
Fair Value, Inputs, Level 2 [Member] | Effectsofnettingandallocationofcollateral1 [Member]      
Equities      
Derivative Asset (9)   (6)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 3,408   3,521
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0   0
Deferred Compensation Liability, Current and Noncurrent (131)   (99)
Financial Liabilities Fair Value Disclosure (389)   (334)
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 3,019   3,187
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (232)   (219)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (4,688)   (3,348)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (79)   (57)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (26)   (16)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (4,535)   (3,186)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (23)   (16)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (8)   (3)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (5)   (3)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]      
Equities      
Derivative Asset 934   902
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 285   326
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 285   326
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 2,307   2,465
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 2,307   2,465
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 13   15
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 13   15
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     1,824
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     1,824
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 45   61
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 45   61
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 34   71
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 34   71
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     0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
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 2,275   2,373
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 2,275   2,373
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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 equivalents     92
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]      
Equities      
Derivative Asset 42   25
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]      
Equities      
Derivative Asset 82   64
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of netting and allocation of collateral [Member]      
Equities      
Derivative Asset (3,997)   (2,629)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest rate and foreign currency derivative assets [Member]      
Equities      
Derivative Asset 59   47
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 64   147
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 64   147
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 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 equivalents 0   17
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 7   5
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 7   5
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   2
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 2   2
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 25   46
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 25   46
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     1
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 27   49
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 27   49
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]      
Equities      
Derivative Asset 4,849   3,467
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]      
Equities      
Derivative Asset 2   5
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effectsofnettingandallocationofcollateral1 [Member]      
Equities      
Derivative Asset (5)   (3)
Fair Value, Inputs, Level 3 [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     0
U.S. Treasury and agencies      
Fixed income subtotal 20    
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Collateral received from counterparties, net of collateral paid to counterparties 151   201
Fair Value, Inputs, Level 3 [Member] | Economic hedge Interest and Currency [Member]      
Equities      
Derivative Asset 0   0
Fair Value, Inputs, Level 3 [Member] | Cash Equivalents NDT [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 243    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 243    
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 1    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 1    
Fair Value, Inputs, Level 3 [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Fair Value, Inputs, Level 3 [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 20   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 20   0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 1,908   1,898
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0   0
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure (361)   (369)
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 1,547   1,529
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (361)   (369)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (1,150)   (1,097)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (37)   (37)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (826)   (765)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]      
Equities      
Derivative Asset 1,143   1,173
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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 684   670
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 684   670
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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     242
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     242
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   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 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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 25   22
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 25   22
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     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 243   242
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 243   242
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 440   428
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 440   428
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 equivalents     0
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]      
Equities      
Derivative Asset 0   0
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 36   33
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 36   33
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]      
Equities      
Derivative Asset 30   30
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of netting and allocation of collateral [Member]      
Equities      
Derivative Asset (675)   (564)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest rate and foreign currency derivative assets [Member]      
Equities      
Derivative Asset 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 equivalents 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 25   22
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 25   22
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]      
Equities      
Derivative Asset 1,788   1,707
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]      
Equities      
Derivative Asset 0   0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effectsofnettingandallocationofcollateral1 [Member]      
Equities      
Derivative Asset 0   0
Exelon Generation Co L L C [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings 225 $ (212)  
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     104
U.S. Treasury and agencies      
Fixed income subtotal 42    
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (166)   (150)
Derivative Liability, Current 177   182
Exelon Generation Co L L C [Member] | Cash Equivalents NDT [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 277    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 277    
Exelon Generation Co L L C [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 2,111    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 2,111    
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 5,170    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 5,170    
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 1,875    
Exelon Generation Co L L C [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Exelon Generation Co L L C [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 17   17
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 17   17
Exelon Generation Co L L C [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 16   13
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 16   13
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 12,918   12,815
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 130    
Deferred Compensation Liability, Current and Noncurrent (30)   (30)
Financial Liabilities Fair Value Disclosure (373)   (362)
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 12,545   12,453
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     2,660
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (320)   (316)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (7,626)   (6,580)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (23)   (16)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (7,450)   (6,391)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (20)   (16)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (8)   (3)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (11)   (12)
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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (16)   (15)
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 285   326
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 285   326
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 10,543   10,345
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 10,543   10,345
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 2,611    
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 1,415   1,338
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 1,415   1,338
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     2,066
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     2,066
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 45   61
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 45   61
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 130   125
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 130   125
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 130    
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 40   35
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 40   35
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 40    
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 85   105
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     4,902
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     4,902
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 4,296   4,328
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 4,296   4,328
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 376   390
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 440   428
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 440   428
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 equivalents     311
Investments, Fair Value Disclosure 9    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 9    
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 440   537
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 440   537
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 376    
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 190   216
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 190   216
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 190    
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 equivalents 35   17
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure 85    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     104
U.S. Treasury and agencies      
Fixed income subtotal 26    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Economic hedge Interest and Currency [Member]      
Equities      
Derivative Asset 0    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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 3,273    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 3,273    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 17   17
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 17   17
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 5,026   4,679
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 130    
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 8   25
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 5,034   4,704
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (8)   (25)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (2,053)   (2,382)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (28)   (33)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (2,089)   (2,440)
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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (11)   (12)
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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (11)   (12)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic hedge Interest and Currency [Member]      
Equities      
Derivative Asset     0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]      
Equities      
Derivative Asset 117   6
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 4,941   4,550
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 4,941   4,550
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents NDT [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 266    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 266    
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 1,402   1,323
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 1,402   1,323
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other fixed income securitites member [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     390
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     125
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     35
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 39   7
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 39   7
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     3,008
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     3,008
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     1,894
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 1,402   1,323
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 1,402   1,323
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 equivalents     219
Investments, Fair Value Disclosure 9    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 9    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]      
Equities      
Derivative Asset 0   0
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedges [Member]      
Equities      
Derivative Asset     1,922
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]      
Equities      
Derivative Asset 31   36
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]      
Equities      
Derivative Asset (1,739)   (1,964)
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]      
Equities      
Derivative Asset 7   7
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    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     216
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 equivalents 35   0
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 1   1
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 1   1
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 3   6
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 3   6
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     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 3   6
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 3   6
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Alternative Investments, Fair Value Disclosure     105
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]      
Equities      
Derivative Asset 1,591    
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]      
Equities      
Derivative Asset 11   10
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effectsofnettingandallocationofcollateral1 [Member]      
Equities      
Derivative Asset (4)   (3)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     0
U.S. Treasury and agencies      
Fixed income subtotal 16    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Proprietary Trading Liabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (144)   (127)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Economic hedge Interest and Currency [Member]      
Equities      
Derivative Asset 20   20
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Commodity Derivative Assets [Member]      
Equities      
Derivative Asset 1,960   2,069
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 1,868    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 1,868    
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 21    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 21    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 16   13
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 16   13
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member]      
Equities      
Derivative Asset 0   0
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 36   33
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 36   33
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Economic Hedges [Member]      
Equities      
Derivative Asset     7,096
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Proprietary Trading [Member]      
Equities      
Derivative Asset 143   130
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Effects of netting and allocation of collateral [Member]      
Equities      
Derivative Asset (6,411)   (5,157)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Interest rate and foreign currency derivative assets [Member]      
Equities      
Derivative Asset 24   29
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Economic Hedging Instrument [Member]      
Equities      
Derivative Asset 8,228    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Proprietary Trading Interest and Currency Derivative [Member]      
Equities      
Derivative Asset 13   15
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Effectsofnettingandallocationofcollateral1 [Member]      
Equities      
Derivative Asset (9)   (6)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 3,308   3,473
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0    
Investments, Fair Value Disclosure 11    
Deferred Compensation Liability, Current and Noncurrent (30)   (30)
Financial Liabilities Fair Value Disclosure (285)   (265)
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 11    
FinancialAssetLiabilitiesNetFairValueDisclosure1 3,023   3,208
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (232)   (219)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (4,688)   (3,348)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (79)   (57)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (23)   (16)
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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (4,535)   (3,186)
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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (20)   (16)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (8)   (3)
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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (5)   (3)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic hedge Interest and Currency [Member]      
Equities      
Derivative Asset     20
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]      
Equities      
Derivative Asset 934   902
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 285   326
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 285   326
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 2,307   2,465
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 2,307   2,465
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 13   15
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 13   15
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     1,824
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     1,824
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 45   61
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 45   61
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 34   71
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 34   71
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     0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
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 2,275   2,373
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 2,275   2,373
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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 equivalents     92
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]      
Equities      
Derivative Asset 0   0
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedges [Member]      
Equities      
Derivative Asset     3,467
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]      
Equities      
Derivative Asset 82   64
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]      
Equities      
Derivative Asset (3,997)   (2,629)
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]      
Equities      
Derivative Asset 17   22
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 64   147
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 64   147
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 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 equivalents 0   17
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 7   5
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 7   5
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   2
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 2   2
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 25   46
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 25   46
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     1
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 27   49
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 27   49
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]      
Equities      
Derivative Asset 4,849    
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]      
Equities      
Derivative Asset 2   5
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effectsofnettingandallocationofcollateral1 [Member]      
Equities      
Derivative Asset (5)   (3)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     0
U.S. Treasury and agencies      
Fixed income subtotal 0    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Economic hedge Interest and Currency [Member]      
Equities      
Derivative Asset 0    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 243    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 243    
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 1    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 1    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 1,888   1,898
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0    
Investments, Fair Value Disclosure 0    
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure (96)   (122)
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
FinancialAssetLiabilitiesNetFairValueDisclosure1 1,792   1,776
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (96)   (122)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (885)   (850)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (37)   (37)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (826)   (765)
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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 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]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic hedge Interest and Currency [Member]      
Equities      
Derivative Asset     0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]      
Equities      
Derivative Asset 1,143   1,173
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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 684   670
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 684   670
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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     242
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     242
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   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 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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 25   22
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 25   22
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     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 243   242
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 243   242
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 440   428
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 440   428
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 equivalents     0
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]      
Equities      
Derivative Asset 0   0
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 36   33
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 36   33
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedges [Member]      
Equities      
Derivative Asset     1,707
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]      
Equities      
Derivative Asset 30   30
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]      
Equities      
Derivative Asset (675)   (564)
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]      
Equities      
Derivative Asset 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 equivalents 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
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 25   22
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 25   22
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]      
Equities      
Derivative Asset 1,788    
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]      
Equities      
Derivative Asset 0   0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effectsofnettingandallocationofcollateral1 [Member]      
Equities      
Derivative Asset 0   0
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 297    
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 168    
Deferred Compensation Liability, Current and Noncurrent 30    
Financial Liabilities Fair Value Disclosure 30    
Equities      
Derivative Asset 0    
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 267    
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0    
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Economic Hedging Instrument Liabilites [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Financial Liabilities Fair Value Disclosure 1    
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (1)    
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Rabbi Trust Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 129    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 129    
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash Equivalents [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 73    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 73    
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 14    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 14    
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 42    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 42    
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1     133
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     42
Deferred Compensation Liability, Current and Noncurrent     30
Financial Liabilities Fair Value Disclosure     30
Equities      
Derivative Asset     18
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1     103
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability     0
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Economic Hedging Instrument Liabilites [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Financial Liabilities Fair Value Disclosure     2
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities     (2)
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Rabbi Trust Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     73
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     73
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Cash Equivalents [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     12
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     12
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     15
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     15
Pepco Holdings, LLC [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     46
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     46
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 241    
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 168    
Deferred Compensation Liability, Current and Noncurrent 0    
Financial Liabilities Fair Value Disclosure 0    
Equities      
Derivative Asset 0    
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 241    
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Economic Hedging Instrument Liabilites [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Financial Liabilities Fair Value Disclosure 1    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (1)    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Rabbi Trust Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 73    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 73    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash Equivalents [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 73    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 73    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1     54
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     42
Deferred Compensation Liability, Current and Noncurrent     0
Financial Liabilities Fair Value Disclosure     0
Equities      
Derivative Asset     0
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1     54
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability     0
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Economic Hedging Instrument Liabilites [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Financial Liabilities Fair Value Disclosure     2
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities     (2)
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Rabbi Trust Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     12
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     12
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Cash Equivalents [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     12
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     12
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 36    
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0    
Deferred Compensation Liability, Current and Noncurrent 30    
Financial Liabilities Fair Value Disclosure 30    
Equities      
Derivative Asset 0    
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 6    
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Economic Hedging Instrument Liabilites [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Financial Liabilities Fair Value Disclosure 0    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash and Cash Equivalents [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Rabbi Trust Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 36    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 36    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 14    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 14    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 22    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 22    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1     42
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     0
Investments, Fair Value Disclosure     0
Deferred Compensation Liability, Current and Noncurrent     30
Financial Liabilities Fair Value Disclosure     30
Equities      
Derivative Asset     0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
FinancialAssetLiabilitiesNetFairValueDisclosure1     12
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability     0
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Economic Hedging Instrument Liabilites [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Financial Liabilities Fair Value Disclosure     0
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities     0
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Rabbi Trust Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     42
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     42
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     15
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     15
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     27
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     27
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 20    
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0    
Deferred Compensation Liability, Current and Noncurrent 0    
Financial Liabilities Fair Value Disclosure 0    
Equities      
Derivative Asset 0    
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 20    
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Economic Hedging Instrument Liabilites [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Financial Liabilities Fair Value Disclosure 0    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash and Cash Equivalents [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Rabbi Trust Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 20    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 20    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 20    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 20    
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1     37
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents     0
Investments, Fair Value Disclosure     0
Deferred Compensation Liability, Current and Noncurrent     0
Financial Liabilities Fair Value Disclosure     0
Equities      
Derivative Asset     18
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
FinancialAssetLiabilitiesNetFairValueDisclosure1     37
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability     0
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Economic Hedging Instrument Liabilites [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Financial Liabilities Fair Value Disclosure     0
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities     0
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Rabbi Trust Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     19
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     19
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
Pepco Holdings, LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     19
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     19
PECO Energy Co [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 3   271
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Cash surrender value of life insurance investments excluded from Rabbi Trust investments     14
PECO Energy Co [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 22   291
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 19   20
Deferred Compensation Liability, Current and Noncurrent (12)   (12)
Financial Liabilities Fair Value Disclosure (12)   (12)
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 19   20
FinancialAssetLiabilitiesNetFairValueDisclosure1 (10)   279
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
PECO Energy Co [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 8   8
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 8   8
PECO Energy Co [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 11   12
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 11   12
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 3   271
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 11   279
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 8   8
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 8   8
FinancialAssetLiabilitiesNetFairValueDisclosure1 (11)   279
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 8   8
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 8   8
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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 equivalents 0   0
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 11   12
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Deferred Compensation Liability, Current and Noncurrent (12)   (12)
Financial Liabilities Fair Value Disclosure (12)   (12)
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 1   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
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 11   12
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 11   12
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 11   12
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 11   12
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0   0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Baltimore Gas and Electric Company [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 43   25
Baltimore Gas and Electric Company [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 47   29
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 4   4
Deferred Compensation Liability, Current and Noncurrent (3)   (4)
Financial Liabilities Fair Value Disclosure (3)   (4)
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 4   4
FinancialAssetLiabilitiesNetFairValueDisclosure1 (44)   25
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Baltimore Gas and Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 4   4
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 4   4
Baltimore Gas and Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 43   25
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 47   29
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 4   4
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 4   4
FinancialAssetLiabilitiesNetFairValueDisclosure1 (47)   29
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 4   4
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 4   4
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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 equivalents 0   0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Deferred Compensation Liability, Current and Noncurrent (3)   (4)
Financial Liabilities Fair Value Disclosure (3)   (4)
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 3   (4)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0   0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 118   70
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 19    
Deferred Compensation Liability, Current and Noncurrent 5   6
Financial Liabilities Fair Value Disclosure (5)   6
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 113   64
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0   0
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Financial Liabilities Fair Value Disclosure 0   0
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Potomac Electric Power Company [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 99   68
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 99   68
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 43   11
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 43   11
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 14   15
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 14   15
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 42   42
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 42   42
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 62   13
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 19   2
Investments, Fair Value Disclosure 0    
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
FinancialAssetLiabilitiesNetFairValueDisclosure1 62   13
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0   0
Potomac Electric Power Company [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]      
Financial Liabilities Fair Value Disclosure 0   0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Potomac Electric Power Company [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 43   11
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 43   11
Potomac Electric Power Company [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]      
Investments, Fair Value Disclosure 43   11
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 43   11
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 36   38
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     0
Deferred Compensation Liability, Current and Noncurrent 5   6
Financial Liabilities Fair Value Disclosure (5)   (6)
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
FinancialAssetLiabilitiesNetFairValueDisclosure1 31   32
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0   0
Potomac Electric Power Company [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]      
Financial Liabilities Fair Value Disclosure 0   0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Potomac Electric Power 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 36   38
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 36   38
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 14   15
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 14   15
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 22   23
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 22   23
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 20   19
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure     0
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
FinancialAssetLiabilitiesNetFairValueDisclosure1 20   19
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0   0
Potomac Electric Power Company [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]      
Financial Liabilities Fair Value Disclosure 0   0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Potomac Electric Power 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 20   19
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 20   19
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 20   19
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 20   19
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0   0
Deferred Compensation Liability, Current and Noncurrent 1   1
Financial Liabilities Fair Value Disclosure (1)   1
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 (1)   (1)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0   0
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Financial Liabilities Fair Value Disclosure 1   2
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (1)   (2)
Delmarva Power and Light Company [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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0   0
Investments, Fair Value Disclosure 0   0
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
FinancialAssetLiabilitiesNetFairValueDisclosure1 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0   0
Delmarva Power and Light Company [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]      
Financial Liabilities Fair Value Disclosure 1   2
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (1)   (2)
Delmarva Power and Light Company [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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0   0
Investments, Fair Value Disclosure     0
Deferred Compensation Liability, Current and Noncurrent 1   1
Financial Liabilities Fair Value Disclosure (1)   1
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
FinancialAssetLiabilitiesNetFairValueDisclosure1 (1)   (1)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0   0
Delmarva Power and Light Company [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]      
Financial Liabilities Fair Value Disclosure 0   0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Delmarva Power and Light 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0   0
Investments, Fair Value Disclosure     0
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
FinancialAssetLiabilitiesNetFairValueDisclosure1 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0   0
Delmarva Power and Light Company [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]      
Financial Liabilities Fair Value Disclosure 0   0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Delmarva Power and Light 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 148   30
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 148   30
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 148   30
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0   0
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Financial Liabilities Fair Value Disclosure 0   0
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Atlantic City Electric Company [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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 148   30
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 148   30
Investments, Fair Value Disclosure 0   0
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
FinancialAssetLiabilitiesNetFairValueDisclosure1 148   30
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0   0
Atlantic City Electric Company [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]      
Financial Liabilities Fair Value Disclosure 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Atlantic City Electric Company [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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0   0
Investments, Fair Value Disclosure     0
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
FinancialAssetLiabilitiesNetFairValueDisclosure1 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0   0
Atlantic City Electric Company [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]      
Financial Liabilities Fair Value Disclosure 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Atlantic City 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0   0
Investments, Fair Value Disclosure     0
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities     0
FinancialAssetLiabilitiesNetFairValueDisclosure1 0   0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Derivative Liability 0   0
Atlantic City Electric Company [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]      
Financial Liabilities Fair Value Disclosure 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]      
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
Atlantic City 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0    
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0    
Commonwealth Edison Co [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0   29
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (239)   (224)
Derivative Liability, Current 26   23
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   29
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Deferred Compensation Liability, Current and Noncurrent (8)   (8)
Financial Liabilities Fair Value Disclosure (273)   (255)
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 273   (226)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (265)   (247)
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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 equivalents 0   29
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   29
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure 0   0
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 0   29
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 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 equivalents 0   0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Deferred Compensation Liability, Current and Noncurrent (8)   (8)
Financial Liabilities Fair Value Disclosure (8)   (8)
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 8   (8)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities 0   0
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Cash equivalents 0   0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]      
FinancialAssetsFairValueDisclosure1 0   0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Deferred Compensation Liability, Current and Noncurrent 0   0
Financial Liabilities Fair Value Disclosure (265)   (247)
U.S. Treasury and agencies      
FinancialAssetLiabilitiesNetFairValueDisclosure1 265   (247)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]      
Mark-to-market derivative liabilities (265)   (247)
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
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities 0   0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]      
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]      
Investments, Fair Value Disclosure 0   0
U.S. Treasury and agencies      
Interest rate and foreign currency derivative liabilities $ 0   $ 0