1.0.0.3 false CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY AND COMPREHENSIVE INCOME (LOSS) (Parenthetical) (Constellation Energy Group, Inc. and Subsidiaries) (USD $) In Millions, except Per Share data false 1 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 false 2 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 false 3 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 4 Reclassification of net losses on hedging instruments from OCI to net income, tax 2 us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentOnDerivativesIncludedInNetIncomeTax us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 true true -898500000 -898.5 false false 2 true true -120200000 -120.2 false false 3 true true -682300000 -682.3 false false No definition available. No authoritative reference available. false 5 Net unrealized loss on hedging instruments, tax 2 us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 251200000 251.2 false false 2 false true 561600000 561.6 false false 3 false true 408200000 408.2 false false No definition available. No authoritative reference available. false 6 Reclassification of net gains (losses) on securities from OCI to net income, tax 2 us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentForSaleOfSecuritiesIncludedInNetIncomeTax us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -24600000 -24.6 false false 2 false true -79100000 -79.1 false false 3 false true 1000000 1.0 false false No definition available. No authoritative reference available. false 7 Net unrealized gains (losses) on securities, tax 2 us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -78200000 -78.2 false false 2 false true 189800000 189.8 false false 3 false true -25500000 -25.5 false false No definition available. No authoritative reference available. false 8 Prior service cost arising during period, tax 2 us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsArisingDuringPeriodTax us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 1000000 1.0 false false 2 false true 4900000 4.9 false false 3 false false 0 0 false false No definition available. No authoritative reference available. false 9 Net gain (loss) arising during period, tax 2 us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -23900000 -23.9 false false 2 false true 229200000 229.2 false false 3 false true -7800000 -7.8 false false No definition available. No authoritative reference available. false 10 Amortization of net actuarial loss, prior service cost, and transition obligation included in net periodic benefit cost, tax 2 ceg_OtherComprehensiveIncomeAmortizationOfNetActuarialLossPriorServiceCostAndTransitionObligationRecognizedInNetPeriodicPensionCostTax ceg false credit duration monetary Tax effect on the adjustment to other comprehensive income for amortization of net actuarial loss, prior service cost and... false false false false false false false false false 1 false true -19800000 -19.8 false false 2 false true -14900000 -14.9 false false 3 false true -15900000 -15.9 false false Tax effect on the adjustment to other comprehensive income for amortization of net actuarial loss, prior service cost and transition obligation recognized as a component of net periodic benefit cost during the period. No authoritative reference available. false 11 Net unrealized gains on nuclear decommissioning trust funds, tax 2 ceg_ReclassificationOfNetGainsOnNuclearDecommissioningTrustFundsFromOCIToNetIncomeTax ceg false credit duration monetary This element represnts the tax effect of the net unrealized gains on nuclear decommissioning trust funds during the reporting... false false false false false false false false false 1 false true 125300000 125.3 false false 2 false false 0 0 false false 3 false false 0 0 false false This element represnts the tax effect of the net unrealized gains on nuclear decommissioning trust funds during the reporting period. No authoritative reference available. false 12 Net unrealized losses on defined benefit plans, tax 2 ceg_NetGainLossOnDefinedBenefitPlansArisingDuringPeriodTax ceg false debit duration monetary This element represents the tax effect of the net unrealized losses on defined benefit plans during the reporting period. false false false false false false false false false 1 false true -94600000 -94.6 false false 2 false false 0 0 false false 3 false false 0 0 false false This element represents the tax effect of the net unrealized losses on defined benefit plans during the reporting period. No authoritative reference available. false 13 Net unrealized gain (loss) on foreign currency translation, tax 2 us-gaap_OtherComprehensiveIncomeForeignCurrencyTranslationAdjustmentTax us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true -2700000 -2.7 false false 2 false true 100000 0.1 false false 3 false true -1800000 -1.8 false false No definition available. No authoritative reference available. false 14 Other comprehensive income, equity investment in CENG, tax 2 ceg_OtherComprehensiveIncomeEquityInvestmentInCENGJointVentureTax ceg false debit duration monetary Tax effect of other comprehensive income related to equity investment in CENG joint venture false false false false false false false false false 1 false true -11700000 -11.7 false false 2 false false 0 0 false false 3 false false 0 0 false false Tax effect of other comprehensive income related to equity investment in CENG joint venture No authoritative reference available. false 15 Other comprehensive income related to other equity method investees, tax 2 ceg_OtherComprehensiveIncomeEquityInvestmentOtherTax ceg false debit duration monetary Tax effect of other comprehensive income related to other equity investments. false false false false false false false false false 1 true true -1300000 -1.3 false false 2 false false 0 0 false false 3 false false 0 0 false false Tax effect of other comprehensive income related to other equity investments. No authoritative reference available. false 16 Dividends Declared Per Common Share (in dollars per share) 2 us-gaap_CommonStockDividendsPerShareDeclared us-gaap true na duration decimal No definition available. false false false false false false false false true 1 true true 0.96 0.96 false false 2 true true 1.91 1.91 false false 3 true true 1.74 1.74 false false No definition available. No authoritative reference available. false 17 Common stock issued and share base awards, issued to MidAmerican Energy Holdings (in shares) 2 ceg_StockIssuedDuringPeriodSharesCommonStockIssuedAndShareBasedAwardsMerger ceg false na duration shares Common stock issued and share base awards, issued to MidAmerican Energy Holdings false false false false false false false false false 1 false false 0 0 false false 2 false true 19897300000 19897.3 false false 3 false false 0 0 false false Common stock issued and share base awards, issued to MidAmerican Energy Holdings No authoritative reference available. false false 3 14 false HundredThousands HundredThousands Hundreds false true