2.2.0.7 true CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY AND COMPREHENSIVE INCOME (LOSS) (Constellation Energy Group, Inc. and Subsidiaries) (USD $) 0040 - Statement - CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY AND COMPREHENSIVE INCOME (LOSS) (Constellation Energy Group, Inc. and Subsidiaries) true false In Millions, except Share data false false 1 USD true false false false us-gaap_CommonStockMember us-gaap_StatementEquityComponentsAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_CommonStockMember us-gaap_StatementEquityComponentsAxis explicitMember Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 2 USD true false false false us-gaap_RetainedEarningsMember us-gaap_StatementEquityComponentsAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_RetainedEarningsMember us-gaap_StatementEquityComponentsAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 3 USD true false false false us-gaap_AccumulatedOtherComprehensiveIncomeMember us-gaap_StatementEquityComponentsAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_AccumulatedOtherComprehensiveIncomeMember us-gaap_StatementEquityComponentsAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 4 USD true false false false us-gaap_NoncontrollingInterestMember us-gaap_StatementEquityComponentsAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_NoncontrollingInterestMember us-gaap_StatementEquityComponentsAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 5 USD true false false false us-gaap_ComprehensiveIncomeMember us-gaap_StatementEquityComponentsAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ComprehensiveIncomeMember us-gaap_StatementEquityComponentsAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 6 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 $ 6 Balance (in shares) at Dec. 31, 2006 4 us-gaap_CommonStockSharesOutstanding us-gaap true na instant No definition available. false false false true false false false false true false false periodstartlabel instant 2007-01-01T00:00:00 0001-01-01T00:00:00 false 1 false true false false 180519000 180519000 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:sharesItemType shares Total number of shares of common stock held by shareholders. May be all or portion of the number of common shares authorized. These shares represent the ownership interest of the common shareholders. Excludes common shares repurchased by the entity and held as Treasury shares. Shares outstanding equals shares issued minus shares held in treasury. Does not include common shares that have been repurchased. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 false 7 Balance at Dec. 31, 2006 4 us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit instant No definition available. false false false true false false false false true false false periodstartlabel instant 2007-01-01T00:00:00 0001-01-01T00:00:00 false 1 true true false false 2738600000 2738.6 true false false 2 true true false false 3474300000 3474.3 true false false 3 true true false false -1603600000 -1603.6 true false false 4 true true false false 284500000 284.5 true false false 5 false false false false 0 0 true false false 6 true true false false 4893800000 4893.8 false false false xbrli:monetaryItemType monetary Total of Stockholders' Equity (deficit) items, net of receivables from officers, directors owners, and affiliates of the entity including portions attributable to both the parent and noncontrolling interests (previously referred to as minority interest), if any. The entity including portions attributable to the parent and noncontrolling interests is sometimes referred to as the economic entity. This excludes temporary equity and is sometimes called permanent equity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 25 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 26 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A3 -Appendix A false 5 Increase (Decrease) in Shareholders' Equity 3 us-gaap_IncreaseDecreaseInStockholdersEquityRollForward 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. false 11 Decrease in noncontrolling interests from deconsolidation 4 ceg_NoncontrollingInterestDecreaseFromDeconsolidation ceg false debit duration Decrease in noncontrolling interest balance as a result of deconsolidating a subsidiary. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false true false false -74100000 -74.1 true false false 5 false false false false 0 0 true false false 6 false true false false -74100000 -74.1 false false false xbrli:monetaryItemType monetary Decrease in noncontrolling interest balance as a result of deconsolidating a subsidiary. No authoritative reference available. false 12 Comprehensive Income (Loss) 4 us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 13 Net income (loss) 5 us-gaap_ProfitLoss us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false true false false 821500000 821.5 true false false 3 false false false false 0 0 true false false 4 false true false false 12000000 12.0 true false false 5 false true false false 833500000 833.5 true false false 6 false true false false 833500000 833.5 false false false xbrli:monetaryItemType monetary The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A1, A4, A5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 5 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(1) false 15 Hedging instruments: 6 us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPeriodIncreaseDecreaseAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 16 Reclassification of net losses on hedging instruments from OCI to net income, net of taxes of $(898.5), $(120.2) and $(682.3) during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentOnDerivativesIncludedInNetIncomeNetOfTax us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 1124800000 1124.8 true false false 4 false false false false 0 0 true false false 5 false true false false 1124800000 1124.8 true false false 6 false true false false 1124800000 1124.8 false false false xbrli:monetaryItemType monetary Net of tax effect of the reclassification adjustment for accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges included in accumulated comprehensive income that was realized in net income during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 18, 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 31, 46 false 17 Net unrealized loss on hedging instruments, net of taxes of $251.2, $561.6 and $408.2 during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false -671100000 -671.1 true false false 4 false false false false 0 0 true false false 5 false true false false -671100000 -671.1 true false false 6 false true false false -671100000 -671.1 false false false xbrli:monetaryItemType monetary Change in accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges, net of tax effect. The after tax effect change includes an entity's share of an equity investee's increase (decrease) in deferred hedging gains or losses. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 20 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 121 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 46 false 18 Available-for-sale securities: 6 us-gaap_OtherComprehensiveIncomeAvailableForSaleSecuritiesAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 19 Reclassification of net gains (losses) on securities from OCI to net income, net of taxes of $(24.6), $(79.1) and $1.0 during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentForSaleOfSecuritiesIncludedInNetIncomeNetOfTax us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false -1600000 -1.6 true false false 4 false false false false 0 0 true false false 5 false true false false -1600000 -1.6 true false false 6 false true false false -1600000 -1.6 false false false xbrli:monetaryItemType monetary Reclassification adjustment for unrealized gains or losses realized upon the sale of securities, after tax. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 18, 19 false 20 Net unrealized (gains) losses on securities, net of taxes of $(78.2), $189.8 and $(25.5) during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 26500000 26.5 true false false 4 false false false false 0 0 true false false 5 false true false false 26500000 26.5 true false false 6 false true false false 26500000 26.5 false false false xbrli:monetaryItemType monetary Appreciation or loss in value (before reclassification adjustment) of the total of unsold securities during the period being reported on, net of tax. Reclassification adjustments include: (1) the unrealized holding gain or loss, net of tax, at the date of the transfer for a debt security from the held-to-maturity category transferred into the available-for-sale category. Also includes the unrealized gain or loss at the date of transfer for a debt security from the available-for-sale category transferred into the held-to-maturity category; (2) the unrealized gains or losses realized upon the sale of securities, after tax; and (3) the unrealized gains or losses realized upon the write-down of securities, after tax. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b false 21 Defined benefit plans: 6 us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 23 Net (gain) loss arising during period, net of taxes of $(23.9), $229.2 and $(7.8) during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 11600000 11.6 true false false 4 false false false false 0 0 true false false 5 false true false false 11600000 11.6 true false false 6 false true false false 11600000 11.6 false false false xbrli:monetaryItemType monetary The accumulated change in the value of either the projected benefit obligation or the plans assets resulting from experience different from that assumed or from a change in an actuarial assumption that has not been recognized in net periodic benefit cost pursuant to FAS 87 and 106, after tax. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 4 -Subparagraph c, d Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 7 -Subparagraph a Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 19, 24 false 24 Amortization of net actuarial loss, prior service cost, and transition obligation included in net periodic benefit cost, net of taxes of $(19.8), $(14.9) and $(15.9) during 2009, 2008 and 2007, respectively 7 ceg_OtherComprehensiveIncomeAmortizationOfNetActuarialLossPriorServiceCostAndTransitionObligationRecognizedInNetPeriodicPensionCostNetOfTax ceg false credit duration The adjustment to other comprehensive income for amortization of net actuarial loss, prior service cost and transition... false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 24600000 24.6 true false false 4 false false false false 0 0 true false false 5 false true false false 24600000 24.6 true false false 6 false true false false 24600000 24.6 false false false xbrli:monetaryItemType monetary 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, after tax. No authoritative reference available. false 25 Deconsolidation of CENG joint venture: 6 ceg_DeconsolidationOfJointVentureAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 28 Net unrealized (gains) losses on foreign currency translation, net of taxes of $(2.7), $0.1 and $(1.8) during 2009, 2008 and 2007, respectively 6 us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPeriodIncreaseDecrease us-gaap true na duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 7000000 7.0 true false false 4 false false false false 0 0 true false false 5 false true false false 7000000 7.0 true false false 6 false true false false 7000000 7.0 false false false xbrli:monetaryItemType monetary Adjustment that results from the process of translating subsidiary financial statements and foreign equity investments into functional currency of the reporting entity, net of tax. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 52 -Paragraph 13, 20, 31 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 14, 17, 19, 26 false 31 Other 6 ceg_OtherComprehensiveIncomeOtherAdjustmentsNetOfTax ceg false credit duration This element represents other adjustments to accumulated comprehensive income during the period, after tax, not otherwise... false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false -10800000 -10.8 true false false 4 false false false false 0 0 true false false 5 false true false false -10800000 -10.8 true false false 6 false true false false -10800000 -10.8 false false false xbrli:monetaryItemType monetary This element represents other adjustments to accumulated comprehensive income during the period, after tax, not otherwise specified in the taxonomy. No authoritative reference available. false 32 Total Comprehensive Income (Loss) 5 us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false false false false 0 0 true false false 2 false true false false 821500000 821.5 true false false 3 false true false false 511000000 511.0 true false false 4 false true false false 12000000 12.0 true false false 5 false true false false 1344500000 1344.5 true false false 6 false true false false 1344500000 1344.5 false false false xbrli:monetaryItemType monetary The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the economic entity, including both controlling (parent) and noncontrolling interests. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, including any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A5 -Appendix A Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a true 34 Effect of adoption of uncertain tax position accounting standard 4 us-gaap_CumulativeEffectOfInitialAdoptionOfFIN48 us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false true false false -7300000 -7.3 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false -7300000 -7.3 false false false xbrli:monetaryItemType monetary Cumulative net-of-tax effect of initial adoption of FIN 48 - Accounting for Uncertainty in Income Taxes on the opening balance of retained earnings. The cumulative-effect adjustment does not include items that would not be recognized in earnings, such as the effect of adopting this Interpretation on tax positions related to business combinations. The amount of that cumulative-effect adjustment is the difference between the net amount of assets and liabilities recognized in the statement of financial position prior to the application of this Interpretation and the net amount of assets and liabilities recognized as a result of applying the provisions of this Interpretation. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Interpretation (FIN) -Number 48 -Paragraph 23, 24 false 35 BGE preference stock dividends 4 us-gaap_DividendsPreferredStockCash us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false true false false -13200000 -13.2 true false false 5 false false false false 0 0 true false false 6 false true false false -13200000 -13.2 false false false xbrli:monetaryItemType monetary Preferred stock cash dividend declared by an entity during the period. This element includes paid and unpaid dividends declared during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 01-6 -Paragraph 14 -Subparagraph l false 36 Common stock dividend declared ($0.96, $1.91 and $1.74 per share during 2009, 2008 and 2007, respectively) 4 us-gaap_DividendsCommonStockCash us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false true false false -368400000 -368.4 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false -368400000 -368.4 false false false xbrli:monetaryItemType monetary Common stock cash dividend declared by an entity during the period. This element includes paid and unpaid dividends declared during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 false 37 Common stock issued and share-based awards 4 ceg_StockIssuedDuringPeriodValueCommonStockIssuedAndShareBasedAwards ceg false credit duration Value of new stock during the period and equity impact of any share-based compensation plan. false false false false false false false false false false false terselabel false 1 false true false false 184200000 184.2 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false 184200000 184.2 false false false xbrli:monetaryItemType monetary Value of new stock during the period and equity impact of any share-based compensation plan. No authoritative reference available. false 38 Common stock issued and share-based awards (in shares) 5 ceg_StockIssuedDuringPeriodSharesCommonStockIssuedAndShareBasedAwards ceg false na duration Number of shares of new stock issued during the period and number of shares issued during the period as a result of any... false false false false false false false false false false false terselabel false 1 false true false false 1789000 1789000 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:sharesItemType shares Number of shares of new stock issued during the period and number of shares issued during the period as a result of any share-based compensation plan. No authoritative reference available. false 39 Common stock purchased 4 us-gaap_StockRepurchasedDuringPeriodValue us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -159500000 -159.5 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false -159500000 -159.5 false false false xbrli:monetaryItemType monetary This element represents the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30, 31 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Chapter 1 -Section B -Paragraph 11A false 40 Common stock purchased (in shares) 5 us-gaap_StockRepurchasedDuringPeriodShares us-gaap true na duration No definition available. false false false false false false false false false false true negated false 1 false true false false -1847000 -1847000 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:sharesItemType shares Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Chapter 1 -Section B -Paragraph 11A false 41 Common stock purchased and retired 4 us-gaap_StockRepurchasedAndRetiredDuringPeriodValue us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -250000000 -250.0 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false -250000000 -250.0 false false false xbrli:monetaryItemType monetary Value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30, 31 -Article 5 false 42 Common stock purchased and retired (in shares) 5 us-gaap_StockRepurchasedAndRetiredDuringPeriodShares us-gaap true na duration No definition available. false false false false false false false false false false true negated false 1 false true false false -2024000 -2024000 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:sharesItemType shares Number of shares that have been repurchased and retired during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30 -Article 5 false 43 Other 4 us-gaap_StockholdersEquityOther us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false true false false -600000 -0.6 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false -600000 -0.6 false false false xbrli:monetaryItemType monetary This element represents movements included in the statement of changes in stockholders' equity which are not separately disclosed or provided for elsewhere in the taxonomy. No authoritative reference available. false 44 Balance (in shares) at Dec. 31, 2007 4 us-gaap_CommonStockSharesOutstanding us-gaap true na instant No definition available. false false false true false false false false false true false periodendlabel instant 2007-12-31T00:00:00 0001-01-01T00:00:00 false 1 false true false false 178437000 178437000 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:sharesItemType shares Total number of shares of common stock held by shareholders. May be all or portion of the number of common shares authorized. These shares represent the ownership interest of the common shareholders. Excludes common shares repurchased by the entity and held as Treasury shares. Shares outstanding equals shares issued minus shares held in treasury. Does not include common shares that have been repurchased. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 false 45 Balance at Dec. 31, 2007 4 us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit instant No definition available. false false false true false false false false false true false periodendlabel instant 2007-12-31T00:00:00 0001-01-01T00:00:00 false 1 false true false false 2513300000 2513.3 true false false 2 false true false false 3919500000 3919.5 true false false 3 false true false false -1092600000 -1092.6 true false false 4 false true false false 209200000 209.2 true false false 5 false false false false 0 0 true false false 6 false true false false 5549400000 5549.4 false false false xbrli:monetaryItemType monetary Total of Stockholders' Equity (deficit) items, net of receivables from officers, directors owners, and affiliates of the entity including portions attributable to both the parent and noncontrolling interests (previously referred to as minority interest), if any. The entity including portions attributable to the parent and noncontrolling interests is sometimes referred to as the economic entity. This excludes temporary equity and is sometimes called permanent equity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 25 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 26 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A3 -Appendix A false 5 Increase (Decrease) in Shareholders' Equity 3 us-gaap_IncreaseDecreaseInStockholdersEquityRollForward 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. false 10 Increase in noncontrolling interests from consolidation of a VIE 4 ceg_IncreaseDecreaseInNoncontrollingInterestsFromConsolidationOfAVariableInterestEntity ceg false credit duration Increase/decrease in balance of noncontrolling interest due to consolidation/deconsolidation of a variable interest entity... false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false true false false 18100000 18.1 true false false 5 false false false false 0 0 true false false 6 false true false false 18100000 18.1 false false false xbrli:monetaryItemType monetary Increase/decrease in balance of noncontrolling interest due to consolidation/deconsolidation of a variable interest entity during the period. A modification of contractual arrangements changed the allocation of economic risks and rewards of the variable interest entity among the variable interest holders. No authoritative reference available. false 12 Comprehensive Income (Loss) 4 us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 13 Net income (loss) 5 us-gaap_ProfitLoss us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false true false false -1314400000 -1314.4 true false false 3 false false false false 0 0 true false false 4 false true false false -4000000 -4.0 true false false 5 false true false false -1318400000 -1318.4 true false false 6 false true false false -1318400000 -1318.4 false false false xbrli:monetaryItemType monetary The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A1, A4, A5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 5 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(1) false 15 Hedging instruments: 6 us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPeriodIncreaseDecreaseAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 16 Reclassification of net losses on hedging instruments from OCI to net income, net of taxes of $(898.5), $(120.2) and $(682.3) during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentOnDerivativesIncludedInNetIncomeNetOfTax us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 200600000 200.6 true false false 4 false false false false 0 0 true false false 5 false true false false 200600000 200.6 true false false 6 false true false false 200600000 200.6 false false false xbrli:monetaryItemType monetary Net of tax effect of the reclassification adjustment for accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges included in accumulated comprehensive income that was realized in net income during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 18, 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 31, 46 false 17 Net unrealized loss on hedging instruments, net of taxes of $251.2, $561.6 and $408.2 during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false -875300000 -875.3 true false false 4 false false false false 0 0 true false false 5 false true false false -875300000 -875.3 true false false 6 false true false false -875300000 -875.3 false false false xbrli:monetaryItemType monetary Change in accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges, net of tax effect. The after tax effect change includes an entity's share of an equity investee's increase (decrease) in deferred hedging gains or losses. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 20 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 121 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 46 false 18 Available-for-sale securities: 6 us-gaap_OtherComprehensiveIncomeAvailableForSaleSecuritiesAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 19 Reclassification of net gains (losses) on securities from OCI to net income, net of taxes of $(24.6), $(79.1) and $1.0 during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentForSaleOfSecuritiesIncludedInNetIncomeNetOfTax us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 81700000 81.7 true false false 4 false false false false 0 0 true false false 5 false true false false 81700000 81.7 true false false 6 false true false false 81700000 81.7 false false false xbrli:monetaryItemType monetary Reclassification adjustment for unrealized gains or losses realized upon the sale of securities, after tax. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 18, 19 false 20 Net unrealized (gains) losses on securities, net of taxes of $(78.2), $189.8 and $(25.5) during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false -197500000 -197.5 true false false 4 false false false false 0 0 true false false 5 false true false false -197500000 -197.5 true false false 6 false true false false -197500000 -197.5 false false false xbrli:monetaryItemType monetary Appreciation or loss in value (before reclassification adjustment) of the total of unsold securities during the period being reported on, net of tax. Reclassification adjustments include: (1) the unrealized holding gain or loss, net of tax, at the date of the transfer for a debt security from the held-to-maturity category transferred into the available-for-sale category. Also includes the unrealized gain or loss at the date of transfer for a debt security from the available-for-sale category transferred into the held-to-maturity category; (2) the unrealized gains or losses realized upon the sale of securities, after tax; and (3) the unrealized gains or losses realized upon the write-down of securities, after tax. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b false 21 Defined benefit plans: 6 us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 22 Prior service cost arising during period, net of taxes of $1.0 and $4.9 during 2009 and 2008, respectively 7 us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false -7200000 -7.2 true false false 4 false false false false 0 0 true false false 5 false true false false -7200000 -7.2 true false false 6 false true false false -7200000 -7.2 false false false xbrli:monetaryItemType monetary The cost of benefit improvement resulting from a plan amendment that occurred during the period, after tax. The cost has not been recognized in net periodic benefit cost pursuant to FAS 87 and 106. A plan amendment includes provisions that grant increased benefits based on services rendered in prior periods. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 19, 24 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 4 -Subparagraph c, d Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph i Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 106 -Paragraph 52 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 7 -Subparagraph a Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 87 -Paragraph 25 false 23 Net (gain) loss arising during period, net of taxes of $(23.9), $229.2 and $(7.8) during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false -339900000 -339.9 true false false 4 false false false false 0 0 true false false 5 false true false false -339900000 -339.9 true false false 6 false true false false -339900000 -339.9 false false false xbrli:monetaryItemType monetary The accumulated change in the value of either the projected benefit obligation or the plans assets resulting from experience different from that assumed or from a change in an actuarial assumption that has not been recognized in net periodic benefit cost pursuant to FAS 87 and 106, after tax. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 4 -Subparagraph c, d Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 7 -Subparagraph a Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 19, 24 false 24 Amortization of net actuarial loss, prior service cost, and transition obligation included in net periodic benefit cost, net of taxes of $(19.8), $(14.9) and $(15.9) during 2009, 2008 and 2007, respectively 7 ceg_OtherComprehensiveIncomeAmortizationOfNetActuarialLossPriorServiceCostAndTransitionObligationRecognizedInNetPeriodicPensionCostNetOfTax ceg false credit duration The adjustment to other comprehensive income for amortization of net actuarial loss, prior service cost and transition... false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 21300000 21.3 true false false 4 false false false false 0 0 true false false 5 false true false false 21300000 21.3 true false false 6 false true false false 21300000 21.3 false false false xbrli:monetaryItemType monetary 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, after tax. No authoritative reference available. false 25 Deconsolidation of CENG joint venture: 6 ceg_DeconsolidationOfJointVentureAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 28 Net unrealized (gains) losses on foreign currency translation, net of taxes of $(2.7), $0.1 and $(1.8) during 2009, 2008 and 2007, respectively 6 us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPeriodIncreaseDecrease us-gaap true na duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false -3100000 -3.1 true false false 4 false false false false 0 0 true false false 5 false true false false -3100000 -3.1 true false false 6 false true false false -3100000 -3.1 false false false xbrli:monetaryItemType monetary Adjustment that results from the process of translating subsidiary financial statements and foreign equity investments into functional currency of the reporting entity, net of tax. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 52 -Paragraph 13, 20, 31 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 14, 17, 19, 26 false 31 Other 6 ceg_OtherComprehensiveIncomeOtherAdjustmentsNetOfTax ceg false credit duration This element represents other adjustments to accumulated comprehensive income during the period, after tax, not otherwise... false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 200000 0.2 true false false 4 false false false false 0 0 true false false 5 false true false false 200000 0.2 true false false 6 false true false false 200000 0.2 false false false xbrli:monetaryItemType monetary This element represents other adjustments to accumulated comprehensive income during the period, after tax, not otherwise specified in the taxonomy. No authoritative reference available. false 32 Total Comprehensive Income (Loss) 5 us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false false false false 0 0 true false false 2 false true false false -1314400000 -1314.4 true false false 3 false true false false -1119200000 -1119.2 true false false 4 false true false false -4000000 -4.0 true false false 5 false true false false -2437600000 -2437.6 true false false 6 false true false false -2437600000 -2437.6 false false false xbrli:monetaryItemType monetary The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the economic entity, including both controlling (parent) and noncontrolling interests. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, including any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A5 -Appendix A Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a true 33 Effect of adoption of fair value measurement accounting standard 4 us-gaap_CumulativeEffectOfInitialAdoptionOfNewAccountingPrinciple us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false true false false 900000 0.9 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false 900000 0.9 false false false xbrli:monetaryItemType monetary Cumulative effect of initial adoption of new accounting principle on beginning retained earnings, net of tax. This element can be used, generally, for the adjustment to retained earnings of a new accounting principle. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 154 -Paragraph 17, 18 false 35 BGE preference stock dividends 4 us-gaap_DividendsPreferredStockCash us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false true false false -13200000 -13.2 true false false 5 false false false false 0 0 true false false 6 false true false false -13200000 -13.2 false false false xbrli:monetaryItemType monetary Preferred stock cash dividend declared by an entity during the period. This element includes paid and unpaid dividends declared during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 01-6 -Paragraph 14 -Subparagraph l false 36 Common stock dividend declared ($0.96, $1.91 and $1.74 per share during 2009, 2008 and 2007, respectively) 4 us-gaap_DividendsCommonStockCash us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false true false false -341300000 -341.3 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false -341300000 -341.3 false false false xbrli:monetaryItemType monetary Common stock cash dividend declared by an entity during the period. This element includes paid and unpaid dividends declared during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 false 37 Common stock issued and share-based awards 4 ceg_StockIssuedDuringPeriodValueCommonStockIssuedAndShareBasedAwards ceg false credit duration Value of new stock during the period and equity impact of any share-based compensation plan. false false false false false false false false false false false terselabel false 1 false true false false 667300000 667.3 true false false 2 false true false false -35800000 -35.8 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false 631500000 631.5 false false false xbrli:monetaryItemType monetary Value of new stock during the period and equity impact of any share-based compensation plan. No authoritative reference available. false 38 Common stock issued and share-based awards (in shares) 5 ceg_StockIssuedDuringPeriodSharesCommonStockIssuedAndShareBasedAwards ceg false na duration Number of shares of new stock issued during the period and number of shares issued during the period as a result of any... false false false false false false false false false false false terselabel false 1 false true false false 21406000 21406000 [1] true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:sharesItemType shares Number of shares of new stock issued during the period and number of shares issued during the period as a result of any share-based compensation plan. No authoritative reference available. false 39 Common stock purchased 4 us-gaap_StockRepurchasedDuringPeriodValue us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false true false false -16100000 -16.1 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false -16100000 -16.1 false false false xbrli:monetaryItemType monetary This element represents the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30, 31 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Chapter 1 -Section B -Paragraph 11A false 40 Common stock purchased (in shares) 5 us-gaap_StockRepurchasedDuringPeriodShares us-gaap true na duration No definition available. false false false false false false false false false false true negated false 1 false true false false -200000 -200000 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:sharesItemType shares Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Chapter 1 -Section B -Paragraph 11A false 42 Common stock purchased and retired (in shares) 5 us-gaap_StockRepurchasedAndRetiredDuringPeriodShares us-gaap true na duration No definition available. false false false false false false false false false false true negated false 1 false true false false -514000 -514000 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:sharesItemType shares Number of shares that have been repurchased and retired during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30 -Article 5 false 43 Other 4 us-gaap_StockholdersEquityOther us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false true false false -200000 -0.2 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false -200000 -0.2 false false false xbrli:monetaryItemType monetary This element represents movements included in the statement of changes in stockholders' equity which are not separately disclosed or provided for elsewhere in the taxonomy. No authoritative reference available. false 44 Balance (in shares) at Dec. 31, 2008 4 us-gaap_CommonStockSharesOutstanding us-gaap true na instant No definition available. false false false true false false false false false true false periodendlabel instant 2008-12-31T00:00:00 0001-01-01T00:00:00 false 1 false true false false 199129000 199129000 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false 199128908 199128908 false false false xbrli:sharesItemType shares Total number of shares of common stock held by shareholders. May be all or portion of the number of common shares authorized. These shares represent the ownership interest of the common shareholders. Excludes common shares repurchased by the entity and held as Treasury shares. Shares outstanding equals shares issued minus shares held in treasury. Does not include common shares that have been repurchased. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 false 45 Balance at Dec. 31, 2008 4 us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit instant No definition available. false false false true false false false false false true false periodendlabel instant 2008-12-31T00:00:00 0001-01-01T00:00:00 false 1 false true false false 3164500000 3164.5 true false false 2 false true false false 2228700000 2228.7 true false false 3 false true false false -2211800000 -2211.8 true false false 4 false true false false 210100000 210.1 true false false 5 false false false false 0 0 true false false 6 false true false false 3391500000 3391.5 false false false xbrli:monetaryItemType monetary Total of Stockholders' Equity (deficit) items, net of receivables from officers, directors owners, and affiliates of the entity including portions attributable to both the parent and noncontrolling interests (previously referred to as minority interest), if any. The entity including portions attributable to the parent and noncontrolling interests is sometimes referred to as the economic entity. This excludes temporary equity and is sometimes called permanent equity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 25 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 26 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A3 -Appendix A false 5 Increase (Decrease) in Shareholders' Equity 3 us-gaap_IncreaseDecreaseInStockholdersEquityRollForward 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. false 8 Contribution from noncontrolling interest 4 ceg_NoncontrollingInterestIncrease ceg false credit duration Increase in noncontrolling interest balance from contribution by noncontrolling interest. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false true false false 8000000 8.0 true false false 5 false false false false 0 0 true false false 6 false true false false 8000000 8.0 false false false xbrli:monetaryItemType monetary Increase in noncontrolling interest balance from contribution by noncontrolling interest. No authoritative reference available. false 9 Other noncontrolling interest activity 4 us-gaap_MinorityInterestPeriodIncreaseDecrease us-gaap true na duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false true false false 400000 0.4 true false false 5 false false false false 0 0 true false false 6 false true false false 400000 0.4 false false false xbrli:monetaryItemType monetary Net increase (decrease) in balance of noncontrolling interest in the subsidiary during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 false 12 Comprehensive Income (Loss) 4 us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 13 Net income (loss) 5 us-gaap_ProfitLoss us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false true false false 4443400000 4443.4 true false false 3 false false false false 0 0 true false false 4 false true false false 60000000 60.0 true false false 5 false true false false 4503400000 4503.4 true false false 6 false true false false 4503400000 4503.4 false false false xbrli:monetaryItemType monetary The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A1, A4, A5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 5 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(1) false 15 Hedging instruments: 6 us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPeriodIncreaseDecreaseAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 16 Reclassification of net losses on hedging instruments from OCI to net income, net of taxes of $(898.5), $(120.2) and $(682.3) during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentOnDerivativesIncludedInNetIncomeNetOfTax us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 1499400000 1499.4 true false false 4 false false false false 0 0 true false false 5 false true false false 1499400000 1499.4 true false false 6 false true false false 1499400000 1499.4 false false false xbrli:monetaryItemType monetary Net of tax effect of the reclassification adjustment for accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges included in accumulated comprehensive income that was realized in net income during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 18, 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 31, 46 false 17 Net unrealized loss on hedging instruments, net of taxes of $251.2, $561.6 and $408.2 during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false -474700000 -474.7 true false false 4 false false false false 0 0 true false false 5 false true false false -474700000 -474.7 true false false 6 false true false false -474700000 -474.7 false false false xbrli:monetaryItemType monetary Change in accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges, net of tax effect. The after tax effect change includes an entity's share of an equity investee's increase (decrease) in deferred hedging gains or losses. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 20 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 121 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 46 false 18 Available-for-sale securities: 6 us-gaap_OtherComprehensiveIncomeAvailableForSaleSecuritiesAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 19 Reclassification of net gains (losses) on securities from OCI to net income, net of taxes of $(24.6), $(79.1) and $1.0 during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentForSaleOfSecuritiesIncludedInNetIncomeNetOfTax us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 25400000 25.4 true false false 4 false false false false 0 0 true false false 5 false true false false 25400000 25.4 true false false 6 false true false false 25400000 25.4 false false false xbrli:monetaryItemType monetary Reclassification adjustment for unrealized gains or losses realized upon the sale of securities, after tax. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 18, 19 false 20 Net unrealized (gains) losses on securities, net of taxes of $(78.2), $189.8 and $(25.5) during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 77700000 77.7 true false false 4 false false false false 0 0 true false false 5 false true false false 77700000 77.7 true false false 6 false true false false 77700000 77.7 false false false xbrli:monetaryItemType monetary Appreciation or loss in value (before reclassification adjustment) of the total of unsold securities during the period being reported on, net of tax. Reclassification adjustments include: (1) the unrealized holding gain or loss, net of tax, at the date of the transfer for a debt security from the held-to-maturity category transferred into the available-for-sale category. Also includes the unrealized gain or loss at the date of transfer for a debt security from the available-for-sale category transferred into the held-to-maturity category; (2) the unrealized gains or losses realized upon the sale of securities, after tax; and (3) the unrealized gains or losses realized upon the write-down of securities, after tax. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b false 21 Defined benefit plans: 6 us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 22 Prior service cost arising during period, net of taxes of $1.0 and $4.9 during 2009 and 2008, respectively 7 us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false -1500000 -1.5 true false false 4 false false false false 0 0 true false false 5 false true false false -1500000 -1.5 true false false 6 false true false false -1500000 -1.5 false false false xbrli:monetaryItemType monetary The cost of benefit improvement resulting from a plan amendment that occurred during the period, after tax. The cost has not been recognized in net periodic benefit cost pursuant to FAS 87 and 106. A plan amendment includes provisions that grant increased benefits based on services rendered in prior periods. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 19, 24 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 4 -Subparagraph c, d Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph i Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 106 -Paragraph 52 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 7 -Subparagraph a Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 87 -Paragraph 25 false 23 Net (gain) loss arising during period, net of taxes of $(23.9), $229.2 and $(7.8) during 2009, 2008 and 2007, respectively 7 us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 26900000 26.9 true false false 4 false false false false 0 0 true false false 5 false true false false 26900000 26.9 true false false 6 false true false false 26900000 26.9 false false false xbrli:monetaryItemType monetary The accumulated change in the value of either the projected benefit obligation or the plans assets resulting from experience different from that assumed or from a change in an actuarial assumption that has not been recognized in net periodic benefit cost pursuant to FAS 87 and 106, after tax. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 4 -Subparagraph c, d Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 7 -Subparagraph a Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 19, 24 false 24 Amortization of net actuarial loss, prior service cost, and transition obligation included in net periodic benefit cost, net of taxes of $(19.8), $(14.9) and $(15.9) during 2009, 2008 and 2007, respectively 7 ceg_OtherComprehensiveIncomeAmortizationOfNetActuarialLossPriorServiceCostAndTransitionObligationRecognizedInNetPeriodicPensionCostNetOfTax ceg false credit duration The adjustment to other comprehensive income for amortization of net actuarial loss, prior service cost and transition... false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 30300000 30.3 true false false 4 false false false false 0 0 true false false 5 false true false false 30300000 30.3 true false false 6 false true false false 30300000 30.3 false false false xbrli:monetaryItemType monetary 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, after tax. No authoritative reference available. false 25 Deconsolidation of CENG joint venture: 6 ceg_DeconsolidationOfJointVentureAbstract 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 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 26 Net unrealized gains on nuclear decommissioning trust funds, net of taxes of $125.3 7 ceg_ReclassificationOfNetGainsOnNuclearDecommissioningTrustFundsFromOCIToNetIncome ceg false debit duration This element represents the net unrealized gains/losses on nuclear decommissioning trust funds, net of taxes during the... false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false -125300000 -125.3 true false false 4 false false false false 0 0 true false false 5 false true false false -125300000 -125.3 true false false 6 false true false false -125300000 -125.3 false false false xbrli:monetaryItemType monetary This element represents the net unrealized gains/losses on nuclear decommissioning trust funds, net of taxes during the reporting period. No authoritative reference available. false 27 Net unrealized losses on defined benefit plans, net of taxes of $(94.6) 7 ceg_NetGainLossOnDefinedBenefitPlansArisingDuringPeriodNetOfTaxes ceg false credit duration This element represents the net unrealized losses on defined benefit plans, net of taxes during the reporting period. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 138000000 138.0 true false false 4 false false false false 0 0 true false false 5 false true false false 138000000 138.0 true false false 6 false true false false 138000000 138.0 false false false xbrli:monetaryItemType monetary This element represents the net unrealized losses on defined benefit plans, net of taxes during the reporting period. No authoritative reference available. false 28 Net unrealized (gains) losses on foreign currency translation, net of taxes of $(2.7), $0.1 and $(1.8) during 2009, 2008 and 2007, respectively 6 us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPeriodIncreaseDecrease us-gaap true na duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 7100000 7.1 true false false 4 false false false false 0 0 true false false 5 false true false false 7100000 7.1 true false false 6 false true false false 7100000 7.1 false false false xbrli:monetaryItemType monetary Adjustment that results from the process of translating subsidiary financial statements and foreign equity investments into functional currency of the reporting entity, net of tax. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 52 -Paragraph 13, 20, 31 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 14, 17, 19, 26 false 29 Other comprehensive income - equity investment in CENG, net of taxes of $(11.7) 6 ceg_OtherComprehensiveIncomeEquityInvestmentInCENGJointVentureNetOfTaxes ceg false credit duration This element represents other comprehensive income related to equity investment in CENG joint venture during the period, net... false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 12900000 12.9 true false false 4 false false false false 0 0 true false false 5 false true false false 12900000 12.9 true false false 6 false true false false 12900000 12.9 false false false xbrli:monetaryItemType monetary This element represents other comprehensive income related to equity investment in CENG joint venture during the period, net of tax. No authoritative reference available. false 30 Other comprehensive income related to other equity method investees, net of taxes of $(1.3) 6 ceg_OtherComprehensiveIncomeEquityInvestmentOtherNetOfTax ceg false credit duration This element represents other comprehensive income related to other equity investments during the period, net of tax. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false true false false 2100000 2.1 true false false 4 false false false false 0 0 true false false 5 false true false false 2100000 2.1 true false false 6 false true false false 2100000 2.1 false false false xbrli:monetaryItemType monetary This element represents other comprehensive income related to other equity investments during the period, net of tax. No authoritative reference available. false 32 Total Comprehensive Income (Loss) 5 us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false false false false 0 0 true false false 2 false true false false 4443400000 4443.4 true false false 3 false true false false 1218300000 1218.3 true false false 4 false true false false 60000000 60.0 true false false 5 false true false false 5721700000 5721.7 true false false 6 false true false false 5721700000 5721.7 false false false xbrli:monetaryItemType monetary The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the economic entity, including both controlling (parent) and noncontrolling interests. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, including any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A5 -Appendix A Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a true 35 BGE preference stock dividends 4 us-gaap_DividendsPreferredStockCash us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false true false false -13200000 -13.2 true false false 5 false false false false 0 0 true false false 6 false true false false -13200000 -13.2 false false false xbrli:monetaryItemType monetary Preferred stock cash dividend declared by an entity during the period. This element includes paid and unpaid dividends declared during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 01-6 -Paragraph 14 -Subparagraph l false 36 Common stock dividend declared ($0.96, $1.91 and $1.74 per share during 2009, 2008 and 2007, respectively) 4 us-gaap_DividendsCommonStockCash us-gaap true debit duration No definition available. false false false false false false false false false false true negated false 1 false false false false 0 0 true false false 2 false true false false -192200000 -192.2 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false -192200000 -192.2 false false false xbrli:monetaryItemType monetary Common stock cash dividend declared by an entity during the period. This element includes paid and unpaid dividends declared during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 false 37 Common stock issued and share-based awards 4 ceg_StockIssuedDuringPeriodValueCommonStockIssuedAndShareBasedAwards ceg false credit duration Value of new stock during the period and equity impact of any share-based compensation plan. false false false false false false false false false false false terselabel false 1 false true false false 65100000 65.1 true false false 2 false true false false -18900000 -18.9 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false 46200000 46.2 false false false xbrli:monetaryItemType monetary Value of new stock during the period and equity impact of any share-based compensation plan. No authoritative reference available. false 38 Common stock issued and share-based awards (in shares) 5 ceg_StockIssuedDuringPeriodSharesCommonStockIssuedAndShareBasedAwards ceg false na duration Number of shares of new stock issued during the period and number of shares issued during the period as a result of any... false false false false false false false false false false false terselabel false 1 false true false false 1856000 1856000 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 false false false xbrli:sharesItemType shares Number of shares of new stock issued during the period and number of shares issued during the period as a result of any share-based compensation plan. No authoritative reference available. false 44 Balance (in shares) at Dec. 31, 2009 4 us-gaap_CommonStockSharesOutstanding us-gaap true na instant No definition available. false false false true false false false false false true false periodendlabel instant 2009-12-31T00:00:00 0001-01-01T00:00:00 false 1 false true false false 200985000 200985000 true false false 2 false false false false 0 0 true false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false 200985414 200985414 false false false xbrli:sharesItemType shares Total number of shares of common stock held by shareholders. May be all or portion of the number of common shares authorized. These shares represent the ownership interest of the common shareholders. Excludes common shares repurchased by the entity and held as Treasury shares. Shares outstanding equals shares issued minus shares held in treasury. Does not include common shares that have been repurchased. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 false 45 Balance at Dec. 31, 2009 4 us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit instant No definition available. false false false true false false false false false true false periodendlabel instant 2009-12-31T00:00:00 0001-01-01T00:00:00 false 1 true true false false 3229600000 3229.6 true false false 2 true true false false 6461000000 6461.0 true false false 3 true true false false -993500000 -993.5 true false false 4 true true false false 265300000 265.3 true false false 5 false false false false 0 0 true false false 6 true true false false 8962400000 8962.4 false false false xbrli:monetaryItemType monetary Total of Stockholders' Equity (deficit) items, net of receivables from officers, directors owners, and affiliates of the entity including portions attributable to both the parent and noncontrolling interests (previously referred to as minority interest), if any. The entity including portions attributable to the parent and noncontrolling interests is sometimes referred to as the economic entity. This excludes temporary equity and is sometimes called permanent equity. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 25 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 26 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A3 -Appendix A false 1 Includes 19,897.3 million shares issued to MidAmerican Energy Holdings Company. 6 88 false HundredThousands NoRounding UnKnown false true