2.2.0.7 false Other Events (Details 2) (USD $) 4021 - Disclosure - Other Events (Details 2) true false 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 $ false 2 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 $ false 3 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 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 $ 3 Gain on Sale of 49.99% Membership Interest in CENG to EDF 1 ceg_MembershipInterestSaleAbstract ceg false 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 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 4 Percent of membership interest in CENG sold (in hundredths) 2 ceg_MembershipInterestSalePercentage ceg false na instant The percentage of ownership interest in a subsidiary that was sold during the period. false false false false false false false false false false false terselabel false 1 false true false false 0.4999 0.4999 false false false 2 false false false false 0 0 false false false 3 false true false false 0.4999 0.4999 false false false us-types:percentItemType pure The percentage of ownership interest in a subsidiary that was sold during the period. No authoritative reference available. false 5 Purchase price of 49.99% membership interest in CENG sold to EDF 2 ceg_MembershipInterestSoldInAffiliates ceg false credit duration This element represents the purchase price received for the sale of a membership interest in a subsidiary. false false false false false false false false false false false terselabel false 1 false false false false 0 0 false false false 2 true true false false 4500000000 4500000000 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary This element represents the purchase price received for the sale of a membership interest in a subsidiary. No authoritative reference available. false 6 Amount of liability recorded in November 2009 as an estimate for the one-time per customer distribution rate credit for BGE's residential customers 2 ceg_OneTimeCustomerDistributionRateCreditFundingAmount ceg false credit duration This element represents the estimated amount of the liability for a one-time per customer distribution rate credit of a... false false false false false false false false false false false terselabel false 1 false true false false 110500000 110500000 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary This element represents the estimated amount of the liability for a one-time per customer distribution rate credit of a subsidiary. No authoritative reference available. false 7 Approximate amount used to estimate the one-time per customer distribution rate credit liability (in dollars per customer) 2 ceg_OneTimeCustomerDistributionRateCreditFundingAmountPerCustomerApproximately ceg false credit duration This element represents the estimated amount to be funded per customer for a one-time per customer distribution rate credit... false false false false false false false false false false false terselabel false 1 false true false false 100 100 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary This element represents the estimated amount to be funded per customer for a one-time per customer distribution rate credit of a subsidiary. No authoritative reference available. false 8 Final amount used to calculate the one-time per customer distribution rate credit liability (in dollars per customer) 2 ceg_OneTimeCustomerDistributionRateCreditFundingAmountPerCustomer ceg false credit duration This element represents the final amount to be funded per customer for a one-time per customer distribution rate credit of a... false false false false false false false false false false false terselabel false 1 false true false false 100 100 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary This element represents the final amount to be funded per customer for a one-time per customer distribution rate credit of a subsidiary. No authoritative reference available. false 9 Additional amount accrued for the one-time customer distribution rate credit liability 2 ceg_OneTimeCustomerDistributionRateCreditAdditionalAmountOnLitigation ceg false credit duration This element represents the additional amount accrued for the one-time per customer distribution rate credit of a subsidiary. false false false false false false false false false false false terselabel false 1 false true false false 1900000 1900000 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary This element represents the additional amount accrued for the one-time per customer distribution rate credit of a subsidiary. No authoritative reference available. false 10 Total amount accrued for the one-time customer distribution rate credit liability 2 ceg_OneTimeCustomerDistributionRateCreditFundingAmountAfterLitigation ceg false credit duration This element represents the total amount accrued for the one-time per customer distribution rate credit of a subsidiary. false false false false false false false false false false false terselabel false 1 false true false false 112400000 112400000 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary This element represents the total amount accrued for the one-time per customer distribution rate credit of a subsidiary. No authoritative reference available. false 11 Equity contribution to BGE to fund the after-tax amount of the rate credit 2 ceg_EquityContributionToSubsidiaryToFundTheAfterTaxAmountOfTheRateCredit ceg false credit duration This element represents an equity contribution made to a subsidiary to fund the after-tax amount of the rate credit as... false false false false false false false false false false false terselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 66000000 66000000 false false false xbrli:monetaryItemType monetary This element represents an equity contribution made to a subsidiary to fund the after-tax amount of the rate credit as ordered by the state public service commission. No authoritative reference available. false 12 Cash capital contribution commitment to BGE 2 ceg_CashCapitalContributionCommitmentToSubsidiary ceg false credit duration This element represents the cash capital contribution required to be made to a subsidiary. false false false false false false false false false false false terselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 250000000 250000000 false false false xbrli:monetaryItemType monetary This element represents the cash capital contribution required to be made to a subsidiary. No authoritative reference available. false 13 Equity ratio below which BGE will not pay common dividends to its holding company (in hundredths) 2 ceg_EquityRatioBelowWhichSubsidiaryWillNotPayCommonDividendsToItsHoldingCompany ceg false na duration This element represents the equity ratio below which the subsidiary is not allowed to pay common dividends to its holding... false false false false false false false false false false false terselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 0.48 0.48 false false false us-types:percentItemType pure This element represents the equity ratio below which the subsidiary is not allowed to pay common dividends to its holding company pursuant to the Maryland PSC's ratemaking precedents. No authoritative reference available. false 14 Number of major credit rating agencies to have assigned below investment grade rating for senior unsecured credit 2 ceg_NumberOfCreditRatingAgenciesAssigningBelowInvestmentGradeRatingToSubsidiariesUnsecuredSeniorCredit ceg false na instant This element represents the number of credit rating agencies, which assign below investment grade rating to subsidiary's... false false false false false false false false false false false terselabel false 1 false true false false 2 2 false false false 2 false false false false 0 0 false false false 3 false true false false 2 2 false false false xbrli:integerItemType integer This element represents the number of credit rating agencies, which assign below investment grade rating to subsidiary's senior unsecured credit. No authoritative reference available. false 15 Aggregate number of major credit rating agencies 2 ceg_AggregateNumberOfCreditRatingAgenciesProvidingRatingToSubsidiariesSeniorUnsecuredCredit ceg false na instant This element represents the aggregate number of credit rating agencies, which rate subsidiary's senior unsecured credit. false false false false false false false false false false false terselabel false 1 false true false false 3 3 false false false 2 false false false false 0 0 false false false 3 false true false false 3 3 false false false xbrli:integerItemType integer This element represents the aggregate number of credit rating agencies, which rate subsidiary's senior unsecured credit. No authoritative reference available. false 16 Cap for rate increase in first electric distribution rate case (in hundredths) 2 ceg_IncreaseInTheFirstElectricDistributionRateCap ceg false na duration This element represents the cap for the rate increase in the first electric distribution rate case as agreed to with the... false false false false false false false false false false false terselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 0.05 0.05 false false false us-types:percentItemType pure This element represents the cap for the rate increase in the first electric distribution rate case as agreed to with the state and public service commission. No authoritative reference available. false 17 Maximum rate of cost allocation to BGE (in hundredths) 2 ceg_MaximumRateOfAllocationToSubsidiary ceg false na duration This element represents the maximum rate of cost allocation to the regulated subsidiary until reviewed in the next rate case. false false false false false false false false false false false terselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 0.31 0.31 false false false us-types:percentItemType pure This element represents the maximum rate of cost allocation to the regulated subsidiary until reviewed in the next rate case. No authoritative reference available. false 18 Cash proceeds from sale of 49.99% membership interest in CENG 2 ceg_ProceedsFromPaymentsForMembershipInterestSale ceg false debit duration This element represents the cash proceeds from the sale of membership interest in joint venture. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 3528700000 3528700000 false false false xbrli:monetaryItemType monetary This element represents the cash proceeds from the sale of membership interest in joint venture. No authoritative reference available. false 19 Redemption of Series B Preferred Stock held by EDF 2 us-gaap_PreferredStockRedemptionAmount 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 1000000000 false false false 2 false false false false 0 0 false false false 3 false true false false 1000000000 1000000000 false false false xbrli:monetaryItemType monetary The redemption (or callable) amount of currently redeemable preferred stock. Includes amounts representing dividends not currently declared or paid but which will be payable under the redemption features or for which ultimate payment is solely within the control of the issuer. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 8 false 20 Carrying amount of CENG's assets and liabilities prior to deconsolidation 2 ceg_NetAssetValueOfDeconsolidatedEntity ceg false debit instant This element represents the net asset value of a deconsolidated entity. false false false false false false false false false false false terselabel false 1 false true false false 2400000000 2400000000 false false false 2 false false false false 0 0 false false false 3 false true false false 2400000000 2400000000 false false false xbrli:monetaryItemType monetary This element represents the net asset value of a deconsolidated entity. No authoritative reference available. false 21 Number of approaches used to determine fair value of an equity method investment 2 ceg_NumberOfApproachesForValuationOfFairValueOfAffiliates ceg false na duration This element represents the number of approaches used to determine the fair value of an equity method investment. false false false false false false false false false false false terselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 3 3 false false false xbrli:integerItemType integer This element represents the number of approaches used to determine the fair value of an equity method investment. No authoritative reference available. false 22 Aggregate amortization of basis difference in investment in CENG 2 ceg_AggregateAmortizationOfBasisDifferenceInInvestmentInAffiliate ceg false credit instant Amount of aggregate amortization of the basis of difference in investment in affiliate as of the balance sheet date. false false false false false false false false false false false terselabel false 1 false true false false 3900000000 3900000000 false false false 2 false false false false 0 0 false false false 3 false true false false 3900000000 3900000000 false false false xbrli:monetaryItemType monetary Amount of aggregate amortization of the basis of difference in investment in affiliate as of the balance sheet date. No authoritative reference available. false 23 Pre-tax gain on sale recognized 2 ceg_PreTaxGainLossOnSaleAbstract ceg false 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 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 24 Fair value of the consideration received from EDF 3 ceg_FairValueConsiderationFromEDF ceg false debit duration This element represents the fair value of the consideration received from EDF. false false false false false false false false false false false terselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 4700000000 4700000000 false false false xbrli:monetaryItemType monetary This element represents the fair value of the consideration received from EDF. No authoritative reference available. false 25 Estimated fair value of our retained interest in CENG 3 us-gaap_EquityMethodInvestmentsFairValueDisclosure us-gaap true debit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 5100000000 5100000000 false false false 2 false false false false 0 0 false false false 3 false true false false 5100000000 5100000000 false false false xbrli:monetaryItemType monetary This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investments accounted for under the equity method of accounting as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 6 -Subparagraph b false 26 Carrying amount of CENG's assets and liabilities prior to deconsolidation 3 ceg_NetAssetValueOfDeconsolidatedEntity ceg false debit instant This element represents the net asset value of a deconsolidated entity. false false false false false false false false false false true negated false 1 false true false false -2400000000 -2400000000 false false false 2 false false false false 0 0 false false false 3 false true false false -2400000000 -2400000000 false false false xbrli:monetaryItemType monetary This element represents the net asset value of a deconsolidated entity. No authoritative reference available. false 27 Pre-tax gain on sale of interest in CENG 3 ceg_GainLossOnSaleOfInterestInCENG ceg false credit duration This element represents the gain (loss) on the sale of a membership interest in a subsidiary. false false false false false false false false false false false totallabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 true true false false 7445600000 7445600000 false false false xbrli:monetaryItemType monetary This element represents the gain (loss) on the sale of a membership interest in a subsidiary. No authoritative reference available. true 3 25 false NoRounding UnKnown UnKnown false true