2.2.0.7 true Leases (Details) (USD $) 4110 - Disclosure - Leases (Details) true false In Millions false false 1 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 $ false 2 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 $ false 3 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 $ 2 Lease Disclosures 2 ceg_LeasesDisclosureLineItems ceg false na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 5 Aggregate lease expense 2 ceg_RentalExpenseForLeasedAssets ceg false debit duration Rental expense incurred for leased assets. false false false false false false false false false false false terselabel false 1 true true false false 422800000 422.8 false false false 2 true true false false 702800000 702.8 false false false 3 true true false false 798800000 798.8 false false false xbrli:monetaryItemType monetary Rental expense incurred for leased assets. 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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 13 -Paragraph 122 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 13 -Paragraph 16 -Subparagraph b(i) true 26 Nonregulated Revenues | Time charter purchase agreements for the use of dry bulk freight vessels 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosureleasesdetails false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false false 4 USD true false false false Nonregulated Revenues ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis xbrldi http://xbrl.org/2006/xbrldi ceg_NonregulatedRevenuesMember ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis explicitMember false false Time charter purchase agreements for the use of dry bulk freight vessels ceg_OperatingLeasesLesseeDisclosureByGroupAxis xbrldi http://xbrl.org/2006/xbrldi ceg_DryBulkFreightVesselsHiredUnderTimeCharterAgreementsMember ceg_OperatingLeasesLesseeDisclosureByGroupAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 5 USD true false false false Nonregulated Revenues ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis xbrldi http://xbrl.org/2006/xbrldi ceg_NonregulatedRevenuesMember ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis explicitMember false false Time charter purchase agreements for the use of dry bulk freight vessels ceg_OperatingLeasesLesseeDisclosureByGroupAxis xbrldi http://xbrl.org/2006/xbrldi ceg_DryBulkFreightVesselsHiredUnderTimeCharterAgreementsMember ceg_OperatingLeasesLesseeDisclosureByGroupAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 41 Sub-Lease Arrangements 2 us-gaap_OperatingLeasesIncomeStatementLeaseRevenueAbstract us-gaap true na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 42 Time charter sub-lease income 2 us-gaap_OperatingLeasesIncomeStatementSubleaseRevenue us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 114000000 114.0 false false false 2 false true false false 289000000 289.0 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary The amount of revenue recognized for the period under subleasing arrangements. 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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 13 -Paragraph 23 -Subparagraph b(ii) true 51 Fuel and purchased energy expenses 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosureleasesdetails false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false false 6 USD true false false false Fuel and purchased energy expenses ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CostOfGoodsAndServicesEnergyCommoditiesAndServicesMember ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 7 USD true false false false Fuel and purchased energy expenses ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CostOfGoodsAndServicesEnergyCommoditiesAndServicesMember ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 8 USD true false false false Fuel and purchased energy expenses ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CostOfGoodsAndServicesEnergyCommoditiesAndServicesMember ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 52 Lease Disclosures 2 ceg_LeasesDisclosureLineItems ceg false na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 55 Aggregate lease expense 2 ceg_RentalExpenseForLeasedAssets ceg false debit duration Rental expense incurred for leased assets. false false false false false false false false false false false terselabel false 1 false true false false 385600000 385.6 false false false 2 false true false false 664800000 664.8 false false false 3 false true false false 758700000 758.7 false false false xbrli:monetaryItemType monetary Rental expense incurred for leased assets. No authoritative reference available. false 76 Operating expenses 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosureleasesdetails false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false false 9 USD true false false false Operating expenses ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis xbrldi http://xbrl.org/2006/xbrldi ceg_OperatingExpenseMember ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 10 USD true false false false Operating expenses ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis xbrldi http://xbrl.org/2006/xbrldi ceg_OperatingExpenseMember ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 11 USD true false false false Operating expenses ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis xbrldi http://xbrl.org/2006/xbrldi ceg_OperatingExpenseMember ceg_OperatingLeaseDisclosureByIncomeStatementLocationAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. 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No authoritative reference available. false 158 Future minimum payments for long-term, noncancelable, operating leases: 2 us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract us-gaap true na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 159 2010 2 us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent us-gaap true credit instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 31500000 31.5 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false xbrli:monetaryItemType monetary For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within one year of the balance sheet date relating to leases defined as operating. 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