2.2.0.7 false Derivatives and Fair Value Measurements (Derivatives Details 4) (USD $) 4133 - Disclosure - Derivatives and Fair Value Measurements (Derivatives Details 4) true false In Millions false false 1 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ 4 Derivatives, Fair Value 2 us-gaap_DerivativesFairValueLineItems us-gaap true na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false xbrli:stringItemType string Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. false 5 Gross fair value of derivative contracts containing a credit-risk related contingent feature 3 ceg_FairValueOfDerivativeWithCreditRiskRelatedContingentFeatureGross ceg false credit instant Represents the gross fair value of out-of-the money derivative contracts containing credit-risk related contingent features... false false false false false false false false false false false terselabel false 1 true true false false 8600000000 8600.0 [1] false false false xbrli:monetaryItemType monetary Represents the gross fair value of out-of-the money derivative contracts containing credit-risk related contingent features that are not fully collateralized by posted cash collateral on an individual, contract-by-contract basis ignoring the effects of master netting arrangements. No authoritative reference available. false 6 Offsetting fair value of in-the-money contracts under master netting arrangements 3 us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral us-gaap true debit instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false -7600000000 -7600.0 [2] false false false xbrli:monetaryItemType monetary The amount as of the balance sheet date of the fair value of derivative assets that in accordance with the entity's accounting policy was offset against an obligation to return cash collateral under a master netting arrangement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FIN39-1 -Paragraph 10B -Subparagraph b false 7 Net fair value of derivative contracts containing a credit-risk related contingent feature 3 us-gaap_DerivativeNetLiabilityPositionAggregateFairValue us-gaap true credit instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 1000000000 1000.0 [3] false false false xbrli:monetaryItemType monetary The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain or loss on that instrument. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44D -Subparagraph b false 8 Cash collateral and letters of credit, collateral posted 3 ceg_CashCollateralAndLettersOfCreditAlreadyPostedAggregateFairValue ceg false debit instant The aggregate amount of cash collateral and letters of credit already posted, at the end of the reporting period, as... false false false false false false false false false false false terselabel false 1 false true false false 700000000 700.0 [4] false false false xbrli:monetaryItemType monetary The aggregate amount of cash collateral and letters of credit already posted, at the end of the reporting period, as collateral for out-of-the-money derivative instruments with credit-risk related contingent features. No authoritative reference available. false 9 Contingent collateral obligation 3 us-gaap_AdditionalCollateralAggregateFairValue us-gaap true debit instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 200000000 200.0 [5] false false false xbrli:monetaryItemType monetary The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44D -Subparagraph c false 10 Cash collateral posted 3 us-gaap_CollateralAlreadyPostedAggregateFairValue us-gaap true debit instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 125600000 125.6 false false false xbrli:monetaryItemType monetary The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44D -Subparagraph c false 11 Letters of credit, collateral posted 3 ceg_LettersOfCreditCollateralAlreadyPostedFairValueDerivativeLiabilities ceg false debit instant The aggregate amount of letters of credit already posted, at the end of the reporting period, as collateral for... false false false false false false false false false false false terselabel false 1 true true false false 585200000 585.2 false false false xbrli:monetaryItemType monetary The aggregate amount of letters of credit already posted, at the end of the reporting period, as collateral for out-of-the-money derivative instruments with credit-risk related contingent features. No authoritative reference available. false 1 Amount represents the gross fair value of out-of-the-money derivative contracts containing credit-risk-related contingent features that are not fully collateralized by posted cash collateral on an individual, contract-by-contract basis ignoring the effects of master netting agreements. 2 Amount represents the offsetting fair value of in-the-money derivative contracts under legally enforceable master netting agreements with the same counterparty, which reduces the amount of any liability for which we potentially could be required to post collateral. 3 Amount represents the net fair value of out-of-the-money derivative contracts containing credit-risk related contingent features after considering the mitigating effects of offsetting positions under master netting arrangements and reflects the actual net liability upon which any potential contingent collateral obligations would be based. 4 Amount includes cash collateral posted of $125.6 million and letters of credit of $585.2 million. 5 Amounts represent the additional collateral that we could be required to post with counterparties, including both cash collateral and letters of credit, in the event of a credit downgrade to below investment grade after giving consideration to offsetting derivative and non-derivative positions under master netting agreements. 1 8 false HundredThousands UnKnown UnKnown false true