1.0.0.3 false CONSOLIDATED STATEMENTS OF CASH FLOWS (Constellation Energy Group, Inc. and Subsidiaries) (USD $) In Millions 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 4 Cash Flows From Operating Activities 2 us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 5 Net (loss) income 3 us-gaap_ProfitLoss us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 true true -91400000 -91.4 false false 2 true true 324400000 324.4 false false No definition available. No authoritative reference available. false 6 Adjustments to reconcile to net cash provided by operating activities 3 us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 7 Depreciation, depletion, and amortization 4 us-gaap_DepreciationDepletionAndAmortization us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 297500000 297.5 false false 2 false true 290200000 290.2 false false No definition available. No authoritative reference available. false 8 Amortization of nuclear fuel 4 ceg_AmortizationOfNuclearFuel ceg false debit duration monetary The expense charged against earnings for the periodic recognition of nuclear fuel costs. false false false false false false false false false 1 false true 67000000 67.0 false false 2 false true 59100000 59.1 false false The expense charged against earnings for the periodic recognition of nuclear fuel costs. No authoritative reference available. false 9 Amortization of energy contracts 4 us-gaap_AmortizationOfPowerContractsEmissionCredits us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -86700000 -86.7 false false 2 false true -117100000 -117.1 false false No definition available. No authoritative reference available. false 10 All other amortization 4 us-gaap_OtherAmortizationOfDeferredCharges us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 74900000 74.9 false false 2 false true 8300000 8.3 false false No definition available. No authoritative reference available. false 11 Accretion of asset retirement obligations 4 us-gaap_AssetRetirementObligationAccretionExpense us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 36100000 36.1 false false 2 false true 33600000 33.6 false false No definition available. No authoritative reference available. false 12 Deferred income taxes 4 us-gaap_DeferredIncomeTaxExpenseBenefit us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -121600000 -121.6 false false 2 false true 39200000 39.2 false false No definition available. No authoritative reference available. false 13 Investment tax credit adjustments 4 us-gaap_InvestmentTaxCredit us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -3000000 -3.0 false false 2 false true -3200000 -3.2 false false No definition available. No authoritative reference available. false 14 Deferred fuel costs 4 us-gaap_IncreaseDecreaseInDeferredFuelCosts us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 32400000 32.4 false false 2 false true 19700000 19.7 false false No definition available. No authoritative reference available. false 15 Defined benefit obligation expense 4 ceg_DefinedBenefitPlanExpenses ceg false debit duration monetary The amount of pension, postemployment, and other (such as medical, dental and life insurance) postretirement benefit costs... false false false false false false false false false 1 false true 64700000 64.7 false false 2 false true 55500000 55.5 false false The amount of pension, postemployment, and other (such as medical, dental and life insurance) postretirement benefit costs recognized during the period for (1) defined benefit plans (periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain or loss on assets, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments) and for (2) defined contribution plans (to the extent that a plan's defined contributions to an individual's account are to be made for periods in which that individual renders services, the net cost for a period shall be the contribution called for in that period; if a plan calls for contributions for periods after an individual retires or terminates, the estimated cost shall be accrued during the employee's service period). No authoritative reference available. false 16 Defined benefit obligation payments 4 ceg_DefinedBenefitObligationPayments ceg false credit duration monetary The amount of cash or cash equivalents contributed during the reporting period by the entity to fund its pension plans and... false false false false false false false false false 1 false true -328600000 -328.6 false false 2 false true -100300000 -100.3 false false The amount of cash or cash equivalents contributed during the reporting period by the entity to fund its pension plans and its nonpension postretirement benefit plans as well as payments to retirees and disabled employees. No authoritative reference available. false 17 Workforce reduction costs 4 us-gaap_SeveranceCosts us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 11200000 11.2 false false 2 false false 0 0 false false No definition available. No authoritative reference available. false 18 Impairment losses and other costs 4 us-gaap_AssetImpairmentCharges us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 95800000 95.8 false false 2 false false 0 0 false false No definition available. No authoritative reference available. false 19 Impairment losses on nuclear decommissioning trust assets 4 ceg_ImpairmentLossesOnNuclearDecommissioningTrustAssets ceg false debit duration monetary Non-cash impairment charge on certain nuclear decommissioning trust fund assets. false false false false false false false false false 1 false true 62400000 62.4 false false 2 false true 12500000 12.5 false false Non-cash impairment charge on certain nuclear decommissioning trust fund assets. No authoritative reference available. false 20 Merger termination and strategic alternatives costs 4 ceg_MergerTerminationAndStrategicAlternativesCostsCashFlowImpact ceg false debit duration monetary The cash flow impact of costs related to a merger and our pursuit of other strategic alternatives to the merger. false false false false false false false false false 1 false true 37200000 37.2 false false 2 false false 0 0 false false The cash flow impact of costs related to a merger and our pursuit of other strategic alternatives to the merger. No authoritative reference available. false 21 Loss (gain) on divestitures 4 ceg_DisposalGroupNotDiscontinuedOperationGainLossOnDisposalCashFlowImpact ceg false credit duration monetary The cash flow impact of the gain (loss) resulting from the sale of a disposal group that is not a discontinued operation. false false false false false false false false false 1 false true 464100000 464.1 false false 2 false true -99200000 -99.2 false false The cash flow impact of the gain (loss) resulting from the sale of a disposal group that is not a discontinued operation. No authoritative reference available. false 22 Gains on termination of contracts 4 us-gaap_GainLossOnContractTermination us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 false false 2 false true -68900000 -68.9 false false No definition available. No authoritative reference available. false 23 Accrual of Maryland settlement agreement credit 4 us-gaap_LossContingencyAccrualCarryingValueProvision us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 false false 2 false true 188200000 188.2 false false No definition available. No authoritative reference available. false 24 Equity in earnings of affiliates less than dividends received 4 us-gaap_IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 18500000 18.5 false false 2 false true 7400000 7.4 false false No definition available. No authoritative reference available. false 25 Derivative contracts classified as financing activities under SFAS No. 149 4 ceg_DerivativeContractsClassifiedAsFinancingActivitiesOperatingActivitiesImpact ceg false debit duration monetary The amount of ongoing cash flows related to certain out-of-the-money acquired contracts that are derivatives and contain an... false false false false false false false false false 1 false true 785300000 785.3 false false 2 false true 500000 0.5 false false The amount of ongoing cash flows related to certain out-of-the-money acquired contracts that are derivatives and contain an other than insignificant financing element. As a result, the cash flows from these contracts are reclassified from cash provided by (used in) operating activities to cash provided by (used in) financing activities in accordance with SFAS No. 149. No authoritative reference available. false 26 Changes in: 4 us-gaap_IncreaseDecreaseInOperatingCapitalAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 27 Accounts receivable, excluding margin 5 ceg_IncreaseDecreaseInAccountsReceivableExcludingMargin ceg false credit duration monetary The net change during the reporting period in amount due within one year (or one business cycle) from customers for the... false false false false false false false false false 1 false true 599200000 599.2 false false 2 false true -521700000 -521.7 false false The net change during the reporting period in amount due within one year (or one business cycle) from customers for the credit sale of goods and services and amounts related to exchange-traded derivatives, excluding margin. No authoritative reference available. false 28 Derivative assets and liabilities, excluding collateral 5 ceg_IncreaseDecreaseInDerivativeAssetsAndLiabilities ceg false credit duration monetary The net change during the reporting period of all assets and liabilities resulting from contracts that meet the criteria of... false false false false false false false false false 1 false true 185200000 185.2 false false 2 false true -700600000 -700.6 false false The net change during the reporting period of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements, excluding collateral. No authoritative reference available. false 29 Net collateral and margin 5 us-gaap_IncreaseDecreaseInDepositOtherAssets us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 1094900000 1094.9 false false 2 false true 525900000 525.9 false false No definition available. No authoritative reference available. false 30 Materials, supplies, and fuel stocks 5 us-gaap_IncreaseDecreaseInInventories us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 323400000 323.4 false false 2 false true -235500000 -235.5 false false No definition available. No authoritative reference available. false 31 Other current assets 5 us-gaap_IncreaseDecreaseInOtherOperatingAssets us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 237000000 237.0 false false 2 false true 11200000 11.2 false false No definition available. No authoritative reference available. false 32 Accounts payable and accrued liabilities 5 us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -786100000 -786.1 false false 2 false true 1051700000 1051.7 false false No definition available. No authoritative reference available. false 33 Other current liabilities 5 us-gaap_IncreaseDecreaseInOtherOperatingLiabilities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -156000000 -156.0 false false 2 false true -247100000 -247.1 false false No definition available. No authoritative reference available. false 34 Other 4 ceg_OtherCashAndNoncashChangesInOperatingActivities ceg false credit duration monetary Transactions that result in no cash inflows or outflows in the period in which they occur, but affect net income and thus are... false false false false false false false false false 1 false true 51000000 51.0 false false 2 false true 6200000 6.2 false false Transactions that result in no cash inflows or outflows in the period in which they occur, but affect net income and thus are removed when calculating net cash flow from operating activities using the indirect method combined with the net change during the reporting period in the value of other assets or liabilities used in operating activities that are not otherwise defined in the taxonomy. This element is used when there is not a more specific and appropriate element. No authoritative reference available. false 35 Net cash provided by operating activities 3 us-gaap_NetCashProvidedByUsedInOperatingActivities us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true 2964400000 2964.4 false false 2 false true 540000000 540.0 false false No definition available. No authoritative reference available. true 36 Cash Flows From Investing Activities 2 us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 37 Investments in property, plant and equipment 3 us-gaap_PaymentsToAcquirePropertyPlantAndEquipment us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -809100000 -809.1 false false 2 false true -869500000 -869.5 false false No definition available. No authoritative reference available. false 38 Asset and business acquisitions, net of cash acquired 3 ceg_AssetAcquisitionsAndBusinessCombinationsNetOfCashAcquired ceg false credit duration monetary The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase, and the... false false false false false false false false false 1 false false 0 0 false false 2 false true -312400000 -312.4 false false The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase, and the acquisition of other tangible assets not otherwise defined in the taxonomy. No authoritative reference available. false 39 Investments in nuclear decommissioning trust fund securities 3 ceg_InvestmentsInNuclearDecommissioningTrustFundSecurities ceg false credit duration monetary Cash outflows for the investment in securities within the nuclear decommissioning trust fund that are classified as cash... false false false false false false false false false 1 false true -233400000 -233.4 false false 2 false true -282700000 -282.7 false false Cash outflows for the investment in securities within the nuclear decommissioning trust fund that are classified as cash flows from investing activities and are reported on a gross basis. No authoritative reference available. false 40 Proceeds from nuclear decommissioning trust fund securities 3 ceg_ProceedsFromNuclearDecommissioningTrustFundSecurities ceg false debit duration monetary Proceeds from the sale of securities within the nuclear decommissioning trust fund that are classified as cash flows from... false false false false false false false false false 1 false true 214700000 214.7 false false 2 false true 264000000 264.0 false false Proceeds from the sale of securities within the nuclear decommissioning trust fund that are classified as cash flows from investing activities and are reported on a gross basis. No authoritative reference available. false 41 Proceeds from sales of investments and other assets 3 us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 80900000 80.9 false false 2 false true 217000000 217.0 false false No definition available. No authoritative reference available. false 42 Contract and portfolio acquisitions 3 ceg_PaymentsForContractAndPortfolioAcquistions ceg false credit duration monetary The net cash outflow for acquired energy purchase and sale agreements. These agreements had contract prices that differed... false false false false false false false false false 1 false true -2153700000 -2153.7 false false 2 false false 0 0 false false The net cash outflow for acquired energy purchase and sale agreements. These agreements had contract prices that differed from market prices at closing, which resulted in cash payments to the counterparty at the acquisition of the agreements. No authoritative reference available. false 43 Decrease (increase) in restricted funds 3 us-gaap_IncreaseDecreaseInRestrictedCash us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 1004400000 1004.4 false false 2 false true -196900000 -196.9 false false No definition available. No authoritative reference available. false 44 Other 3 us-gaap_PaymentsForProceedsFromOtherInvestingActivities us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -1800000 -1.8 false false 2 false true 12900000 12.9 false false No definition available. No authoritative reference available. false 45 Net cash used in investing activities 3 us-gaap_NetCashProvidedByUsedInInvestingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -1898000000 -1898.0 false false 2 false true -1167600000 -1167.6 false false No definition available. No authoritative reference available. true 46 Cash Flows From Financing Activities 2 us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 47 Net (repayment) issuance of short-term borrowings 3 us-gaap_ProceedsFromRepaymentsOfShortTermDebt us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -515800000 -515.8 false false 2 false true 103700000 103.7 false false No definition available. No authoritative reference available. false 48 Proceeds from issuance of common stock 3 us-gaap_ProceedsFromIssuanceOfCommonStock us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 13600000 13.6 false false 2 false true 8300000 8.3 false false No definition available. No authoritative reference available. false 49 Proceeds from issuance of long-term debt 3 us-gaap_ProceedsFromIssuanceOfLongTermDebt us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 109000000 109.0 false false 2 false true 1100000000 1100.0 false false No definition available. No authoritative reference available. false 50 Repayment of long-term debt 3 us-gaap_RepaymentsOfLongTermDebt us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -1180300000 -1180.3 false false 2 false true -265100000 -265.1 false false No definition available. No authoritative reference available. false 51 Debt issuance costs 3 us-gaap_PaymentsOfDebtIssuanceCosts us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -62800000 -62.8 false false 2 false true -15600000 -15.6 false false No definition available. No authoritative reference available. false 52 Common stock dividends paid 3 us-gaap_PaymentsOfDividendsCommonStock us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -133700000 -133.7 false false 2 false true -165000000 -165.0 false false No definition available. No authoritative reference available. false 53 BGE preference stock dividends paid 3 us-gaap_PaymentsOfDividendsPreferredStockAndPreferenceStock us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -6600000 -6.6 false false 2 false true -6600000 -6.6 false false No definition available. No authoritative reference available. false 54 Proceeds from contract and portfolio acquisitions 3 ceg_ProceedsFromContractAndPortfolioAcquisitions ceg false debit duration monetary The net cash inflow for acquired energy purchase and sale agreements. These agreements had contract prices that differed from... false false false false false false false false false 1 false true 2243100000 2243.1 false false 2 false false 0 0 false false The net cash inflow for acquired energy purchase and sale agreements. These agreements had contract prices that differed from market prices at closing, which resulted in cash payments from the counterparty at the acquisition of the agreements. No authoritative reference available. false 55 Derivative contracts classified as financing activiites under SFAS No. 149 3 ceg_DerivativeContractsClassifiedAsFinancingActivityFinancingActivitiesImpact ceg false debit duration monetary The amount of ongoing cash flows related to certain out-of-the-money acquired contracts that are derivatives and contain a... false false false false false false false false false 1 false true -785300000 -785.3 false false 2 false true -500000 -0.5 false false The amount of ongoing cash flows related to certain out-of-the-money acquired contracts that are derivatives and contain a financing element. As a result, the cash flows from these contracts are reclassified from cash provided by (used in) operating activities to cash provided by (used in) financing activities in accordance with SFAS No. 149. No authoritative reference available. false 56 Other 3 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 11800000 11.8 false false 2 false true 3200000 3.2 false false No definition available. No authoritative reference available. false 57 Net cash (used in) provided by financing activities 3 us-gaap_NetCashProvidedByUsedInFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -307000000 -307.0 false false 2 false true 762400000 762.4 false false No definition available. No authoritative reference available. true 58 Net Increase in Cash and Cash Equivalents 2 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true 759400000 759.4 false false 2 false true 134800000 134.8 false false No definition available. No authoritative reference available. true 59 Cash and Cash Equivalents at Beginning of Period 2 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false true false false 1 false true 202200000 202.2 false false 2 false true 1095900000 1095.9 false false No definition available. No authoritative reference available. false 60 Cash and Cash Equivalents at End of Period 2 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false false true false 1 true true 961600000 961.6 false false 2 true true 1230700000 1230.7 false false No definition available. No authoritative reference available. false false 2 57 false HundredThousands UnKnown UnKnown false true