2.2.0.7 true Capitalization (Details 4) (USD $) 4093 - Disclosure - Capitalization (Details 4) true false In Millions, except Share data, unless otherwise specified 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 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 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 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares 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 $ 2 Capitalization disclosures 2 us-gaap_ScheduleOfCapitalizationLineItems 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 2 false false false false 0 0 false false false 3 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 3 Total Long-term Debt Issued 2 us-gaap_ProceedsFromIssuanceOfLongTermDebt us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 true true false false 136100000 136.1 false false false 2 true true false false 3211400000 3211.4 false false false 3 true true false false 698200000 698.2 false false false xbrli:monetaryItemType monetary The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 19 -Subparagraph b false 9 6.20% deferrable interest subordinated debentures due October 15, 2043 to wholly owned BGE Capital Trust II relating to trust preferred securities 2 ceg_DeferrableInterestSubordinatedDebenturesRelatedToTrustPreferredSecurities ceg false credit instant Carrying value of deferrable interest subordinated debentures related to trust preferred securities as of the balance sheet... false false false false false false false false false false false verboselabel false 1 false true false false 257700000 257.7 false false false 2 false true false false 257700000 257.7 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary Carrying value of deferrable interest subordinated debentures related to trust preferred securities as of the balance sheet date. No authoritative reference available. false 14 Baltimore Gas and Electric Company 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurecapitalizationdetails4 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 false 4 USD true false false false Baltimore Gas and Electric Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 $ na No definition available. No authoritative reference available. false 15 Capitalization disclosures 2 us-gaap_ScheduleOfCapitalizationLineItems 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 2 false false false false 0 0 false false false 3 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 17 Term of BGE's residential electric customers to pay a usage-based, non-bypassable charge securing the rate stabilization bonds (in years) 2 ceg_TermToPayUsageBasedNonbypassableChargeYears ceg false na duration This element represents the term that residential electric customers have to pay a usage-based, non-bypassable charge... false false false false false false false false false false false terselabel false 1 false true false false 10 10 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:decimalItemType decimal This element represents the term that residential electric customers have to pay a usage-based, non-bypassable charge securing rate stabilization bonds, in years. No authoritative reference available. false 20 BGE's transfer of tax-exempt debt to Generation business 2 ceg_TransferOfDebtFromSubsidiaryToParentCompany ceg false credit instant This element represents the transfer of tax-exempt bonds from a subsidiary to the parent company related to the transfer of... false false false false false false false false false false false terselabel false 1 false true false false 278000000 278.0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary This element represents the transfer of tax-exempt bonds from a subsidiary to the parent company related to the transfer of generating assets from the subsidiary to the parent company. No authoritative reference available. false 24 BGE's contingent liability for tax-exempt debt transferred to Generation business 2 ceg_ContingentAmountOfDebtTransferredFromSubsidiaryToParentCompany ceg false credit instant This element represents the outstanding amount of tax-exempt debt transferred from a subsidiary to its parent company for... false false false false false false false false false false false terselabel false 1 false true false false 20000000 20.0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary This element represents the outstanding amount of tax-exempt debt transferred from a subsidiary to its parent company for which the subsidiary remains contingently liable. No authoritative reference available. false 27 BGE Capital Trust II 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurecapitalizationdetails4 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 false 5 USD true false false false BGE Capital Trust II dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi ceg_BGECapitalTrustIIMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ na No definition available. No authoritative reference available. false 28 Capitalization disclosures 2 us-gaap_ScheduleOfCapitalizationLineItems 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 2 false false false false 0 0 false false false 3 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 34 Preferred stock, issued (in shares) 2 us-gaap_PreferredStockSharesIssued us-gaap true na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 10000000 10000000 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:sharesItemType shares Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 false 36 Preferred stock distribution rate (in hundredths) 2 ceg_PreferredStockDividendRatePercentage ceg false na instant The percentage rate used to calculate dividend payments on preferred stock. false false false false false false false false false false false verboselabel false 1 false true false false 0.0620 0.0620 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false us-types:percentItemType pure The percentage rate used to calculate dividend payments on preferred stock. No authoritative reference available. false 38 Issuance of trust preferred securities in 2003 2 ceg_IssuanceOfTrustPreferredSecurities ceg false debit duration This element represents the issuance of trust preferred securities. false false false false false false false false false false false terselabel false 1 false true false false 250000000 250.0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary This element represents the issuance of trust preferred securities. No authoritative reference available. false 39 Liquidation amount per preferred security in addition to accrued but unpaid distributions (in dollars per share) 2 us-gaap_PreferredStockLiquidationPreference us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel true 1 true true false false 25 25 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false us-types:perShareItemType decimal The per share liquidation preference (or restrictions) of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph d -Article 4 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 4, 6 false 40 Bond Co 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurecapitalizationdetails4 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 false 6 USD true false false false Bond Co dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi ceg_BondCoMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 7 USD true false false false Bond Co dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi ceg_BondCoMember dei_LegalEntityAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 8 USD true false false false Bond Co dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi ceg_BondCoMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 41 Capitalization disclosures 2 us-gaap_ScheduleOfCapitalizationLineItems 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 2 false false false false 0 0 false false false 3 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 42 Total Long-term Debt Issued 2 us-gaap_ProceedsFromIssuanceOfLongTermDebt us-gaap true debit duration No definition available. 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 623200000 623.2 false false false xbrli:monetaryItemType monetary The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 19 -Subparagraph b false 43 Term of BGE's residential electric customers to pay a usage-based, non-bypassable charge securing the rate stabilization bonds (in years) 2 ceg_TermToPayUsageBasedNonbypassableChargeYears ceg false na duration This element represents the term that residential electric customers have to pay a usage-based, non-bypassable charge... 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 false false false 0 0 false false false xbrli:decimalItemType decimal This element represents the term that residential electric customers have to pay a usage-based, non-bypassable charge securing rate stabilization bonds, in years. No authoritative reference available. false 51 Issuance of trust preferred securities in 2003 2 ceg_IssuanceOfTrustPreferredSecurities ceg false debit duration This element represents the issuance of trust preferred securities. 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 false false false 0 0   false false false xbrli:monetaryItemType monetary This element represents the issuance of trust preferred securities. No authoritative reference available. false 53 Bond Co | 5.47% Rate Stabilization Bonds maturing in October 2012 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurecapitalizationdetails4 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 false 9 USD true false false false Bond Co dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi ceg_BondCoMember dei_LegalEntityAxis explicitMember false false 5.47% Rate Stabilization Bonds maturing in October 2012 us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi ceg_RateStabilizationBonds5.47PercentMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 54 Capitalization disclosures 2 us-gaap_ScheduleOfCapitalizationLineItems 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 2 false false false false 0 0 false false false 3 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 57 Interest rate (in hundredths) 2 us-gaap_DebtInstrumentInterestRateAtPeriodEnd us-gaap true na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 0.0547 0.0547 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false us-types:percentItemType pure The effective interest rate at the end of the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 58 Rate stabilization bonds 2 us-gaap_SecuredLongTermDebt 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 171700000 171.7 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 Carrying value as of the balance sheet date of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer), excluding the current portion, if any. Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 66 Bond Co | 5.72% Rate Stabilization Bonds maturing in April 2016 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurecapitalizationdetails4 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 false 10 USD true false false false Bond Co dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi ceg_BondCoMember dei_LegalEntityAxis explicitMember false false 5.72% Rate Stabilization Bonds maturing in April 2016 us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi ceg_RateStabilizationBonds5.72PercentMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 67 Capitalization disclosures 2 us-gaap_ScheduleOfCapitalizationLineItems 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 2 false false false false 0 0 false false false 3 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 70 Interest rate (in hundredths) 2 us-gaap_DebtInstrumentInterestRateAtPeriodEnd us-gaap true na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 0.0572 0.0572 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false us-types:percentItemType pure The effective interest rate at the end of the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 71 Rate stabilization bonds 2 us-gaap_SecuredLongTermDebt 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 220000000 220.0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary Carrying value as of the balance sheet date of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer), excluding the current portion, if any. Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 79 Bond Co | 5.82% Rate Stabilization Bonds maturing in April 2017 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurecapitalizationdetails4 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 false 11 USD true false false false Bond Co dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi ceg_BondCoMember dei_LegalEntityAxis explicitMember false false 5.82% Rate Stabilization Bonds maturing in April 2017 us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi ceg_RateStabilizationBonds5.82PercentMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 80 Capitalization disclosures 2 us-gaap_ScheduleOfCapitalizationLineItems 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 2 false false false false 0 0 false false false 3 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 83 Interest rate (in hundredths) 2 us-gaap_DebtInstrumentInterestRateAtPeriodEnd us-gaap true na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 0.0582 0.0582 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false us-types:percentItemType pure The effective interest rate at the end of the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 84 Rate stabilization bonds 2 us-gaap_SecuredLongTermDebt us-gaap true credit instant No definition available. false false false false false false false false false false false terselabel false 1 true true false false 119200000 119.2 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 Carrying value as of the balance sheet date of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer), excluding the current portion, if any. Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower. 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