2.2.0.7 true Derivatives and Fair Value Measurements (Derivatives Details 3) (USD $) 4132 - Disclosure - Derivatives and Fair Value Measurements (Derivatives Details 3) true false In Millions, unless otherwise specified false false 1 USD true false false false Power contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_PowerContractsMember us-gaap_DerivativeByNatureAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 $ 1 Power contracts 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 1 USD true false false false Power contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_PowerContractsMember us-gaap_DerivativeByNatureAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 $ na No definition available. No authoritative reference available. false 2 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 3 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 41.7 41.7 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 4 Derivative, underlying basis 2 us-gaap_DerivativeUnderlyingBasis 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 MWH false false false xbrli:stringItemType string Reference to the index or unit of measurement for the underlying which establishes the pricing terms of the derivative instrument. For example, the basis on the underlying for a natural gas futures contract might be the NYMEX price per million British thermal units (MMBtu). No authoritative reference available. false 6 Power contracts | 2010 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 2 true false false false Power contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_PowerContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2010 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CurrentYearMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 7 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 8 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 32.7 32.7 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 11 Power contracts | 2011 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 3 true false false false Power contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_PowerContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2011 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_OneYearFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 12 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 13 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 1.6 1.6 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 16 Power contracts | 2012 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 4 true false false false Power contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_PowerContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2012 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanOneAndWithinTwoYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 17 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 18 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 3.2 3.2 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 21 Power contracts | 2013 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 5 true false false false Power contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_PowerContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2013 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanTwoAndWithinThreeYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 22 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 23 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 3.2 3.2 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 26 Power contracts | 2014 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 6 true false false false Power contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_PowerContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2014 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanThreeAndWithinFourYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 27 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 28 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 0.1 0.1 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 31 Power contracts | Thereafter 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 7 true false false false Power contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_PowerContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false Thereafter ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi ceg_MoreThanFourYearsFromBalanceSheetDateAndThereafterMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 32 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 33 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 0.9 0.9 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 36 Gas contracts 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 8 USD true false false false Gas contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_GasContractsMember us-gaap_DerivativeByNatureAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 $ na No definition available. No authoritative reference available. false 37 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 38 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 161.8 161.8 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 39 Derivative, underlying basis 2 us-gaap_DerivativeUnderlyingBasis 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 mmBTU false false false xbrli:stringItemType string Reference to the index or unit of measurement for the underlying which establishes the pricing terms of the derivative instrument. For example, the basis on the underlying for a natural gas futures contract might be the NYMEX price per million British thermal units (MMBtu). No authoritative reference available. false 41 Gas contracts | 2010 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 9 true false false false Gas contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_GasContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2010 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CurrentYearMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 42 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 43 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 37.3 37.3 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 46 Gas contracts | 2011 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 10 true false false false Gas contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_GasContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2011 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_OneYearFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 47 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 48 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 37.4 37.4 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 51 Gas contracts | 2012 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 11 true false false false Gas contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_GasContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2012 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanOneAndWithinTwoYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 52 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 53 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 22.1 22.1 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 56 Gas contracts | 2013 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 12 true false false false Gas contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_GasContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2013 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanTwoAndWithinThreeYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 57 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 58 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 21.0 21.0 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 61 Gas contracts | 2014 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 13 true false false false Gas contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_GasContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2014 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanThreeAndWithinFourYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 62 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 63 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 22.7 22.7 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 66 Gas contracts | Thereafter 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 14 true false false false Gas contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_GasContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false Thereafter ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi ceg_MoreThanFourYearsFromBalanceSheetDateAndThereafterMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 67 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 68 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 21.3 21.3 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 71 Coal contracts 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 15 USD true false false false Coal contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CoalContractsMember us-gaap_DerivativeByNatureAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 $ na No definition available. No authoritative reference available. false 72 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 73 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 8.0 8.0 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 74 Derivative, underlying basis 2 us-gaap_DerivativeUnderlyingBasis 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 Tons false false false xbrli:stringItemType string Reference to the index or unit of measurement for the underlying which establishes the pricing terms of the derivative instrument. For example, the basis on the underlying for a natural gas futures contract might be the NYMEX price per million British thermal units (MMBtu). No authoritative reference available. false 76 Coal contracts | 2010 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 16 true false false false Coal contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CoalContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2010 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CurrentYearMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 77 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 78 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 3.9 3.9 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 81 Coal contracts | 2011 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 17 true false false false Coal contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CoalContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2011 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_OneYearFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 82 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 83 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 3.9 3.9 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 86 Coal contracts | 2012 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 18 true false false false Coal contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CoalContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2012 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanOneAndWithinTwoYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 87 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 88 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 0.2 0.2 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 91 Interest rate contracts 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 19 USD true false false false Interest rate contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_InterestRateContractMember us-gaap_DerivativeByNatureAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 92 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 95 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 true true false false 2066600000 2066.6 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 96 Interest rate contracts | 2010 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 20 USD true false false false Interest rate contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_InterestRateContractMember us-gaap_DerivativeByNatureAxis explicitMember false false 2010 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CurrentYearMember ceg_DerivativeSettlementYearAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 97 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 100 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 972300000 972.3 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 101 Interest rate contracts | 2011 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 21 USD true false false false Interest rate contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_InterestRateContractMember us-gaap_DerivativeByNatureAxis explicitMember false false 2011 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_OneYearFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 102 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 105 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 140600000 140.6 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 106 Interest rate contracts | 2012 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 22 USD true false false false Interest rate contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_InterestRateContractMember us-gaap_DerivativeByNatureAxis explicitMember false false 2012 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanOneAndWithinTwoYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 107 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 110 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 440500000 440.5 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 111 Interest rate contracts | 2013 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 23 USD true false false false Interest rate contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_InterestRateContractMember us-gaap_DerivativeByNatureAxis explicitMember false false 2013 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanTwoAndWithinThreeYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 112 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 115 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 58200000 58.2 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 116 Interest rate contracts | 2014 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 24 USD true false false false Interest rate contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_InterestRateContractMember us-gaap_DerivativeByNatureAxis explicitMember false false 2014 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanThreeAndWithinFourYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 117 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 120 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 255000000 255.0 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 121 Interest rate contracts | Thereafter 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 25 USD true false false false Interest rate contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_InterestRateContractMember us-gaap_DerivativeByNatureAxis explicitMember false false Thereafter ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi ceg_MoreThanFourYearsFromBalanceSheetDateAndThereafterMember ceg_DerivativeSettlementYearAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 122 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 125 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 200000000 200.0 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 126 Oil contracts 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 26 true false false false Oil contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_OilContractsMember us-gaap_DerivativeByNatureAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 127 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 128 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 0.3 0.3 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 129 Derivative, underlying basis 2 us-gaap_DerivativeUnderlyingBasis 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 BBL false false false xbrli:stringItemType string Reference to the index or unit of measurement for the underlying which establishes the pricing terms of the derivative instrument. For example, the basis on the underlying for a natural gas futures contract might be the NYMEX price per million British thermal units (MMBtu). No authoritative reference available. false 131 Oil contracts | 2010 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 27 true false false false Oil contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_OilContractsMember us-gaap_DerivativeByNatureAxis explicitMember false false 2010 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CurrentYearMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 132 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 133 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 0.3 0.3 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 136 Emission allowances 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 28 true false false false Emission allowances us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_EmmissionAllowancesMember us-gaap_DerivativeByNatureAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 137 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 138 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 7.2 7.2 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 139 Derivative, underlying basis 2 us-gaap_DerivativeUnderlyingBasis 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 Tons false false false xbrli:stringItemType string Reference to the index or unit of measurement for the underlying which establishes the pricing terms of the derivative instrument. For example, the basis on the underlying for a natural gas futures contract might be the NYMEX price per million British thermal units (MMBtu). No authoritative reference available. false 141 Emission allowances | 2010 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 29 true false false false Emission allowances us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi ceg_EmmissionAllowancesMember us-gaap_DerivativeByNatureAxis explicitMember false false 2010 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CurrentYearMember ceg_DerivativeSettlementYearAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 142 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 143 Notional amount, non-monetary 2 invest_DerivativeNonmonetaryNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 7.2 7.2 [1] false false false xbrli:decimalItemType decimal Aggregate notional amount of derivative expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract. No authoritative reference available. false 146 Foreign exchange contracts 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 30 USD true false false false Foreign exchange contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ForeignExchangeContractMember us-gaap_DerivativeByNatureAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 147 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 150 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 166000000 166.0 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 151 Foreign exchange contracts | 2010 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 31 USD true false false false Foreign exchange contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ForeignExchangeContractMember us-gaap_DerivativeByNatureAxis explicitMember false false 2010 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi ceg_CurrentYearMember ceg_DerivativeSettlementYearAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 152 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 155 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 27900000 27.9 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 156 Foreign exchange contracts | 2011 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 32 USD true false false false Foreign exchange contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ForeignExchangeContractMember us-gaap_DerivativeByNatureAxis explicitMember false false 2011 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_OneYearFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 157 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 160 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 72400000 72.4 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 161 Foreign exchange contracts | 2012 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 33 USD true false false false Foreign exchange contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ForeignExchangeContractMember us-gaap_DerivativeByNatureAxis explicitMember false false 2012 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanOneAndWithinTwoYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 162 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 165 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 16700000 16.7 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 166 Foreign exchange contracts | 2013 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 34 USD true false false false Foreign exchange contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ForeignExchangeContractMember us-gaap_DerivativeByNatureAxis explicitMember false false 2013 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanTwoAndWithinThreeYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 167 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 170 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 16700000 16.7 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 171 Foreign exchange contracts | 2014 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 35 USD true false false false Foreign exchange contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ForeignExchangeContractMember us-gaap_DerivativeByNatureAxis explicitMember false false 2014 ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_MoreThanThreeAndWithinFourYearsFromBalanceSheetDateMember ceg_DerivativeSettlementYearAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 172 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 175 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 false true false false 16800000 16.8 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 176 Foreign exchange contracts | Thereafter 0 na true na na No definition available. false true false false false false false false false false false http://www.constellation.com/role/disclosurederivativeinstrumentsdetails3 false 1 false false false false 0 0 false false false false 36 USD true false false false Foreign exchange contracts us-gaap_DerivativeByNatureAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ForeignExchangeContractMember us-gaap_DerivativeByNatureAxis explicitMember false false Thereafter ceg_DerivativeSettlementYearAxis xbrldi http://xbrl.org/2006/xbrldi ceg_MoreThanFourYearsFromBalanceSheetDateAndThereafterMember ceg_DerivativeSettlementYearAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 177 Volume of derivative activities, by contract type and contractual settlement year 2 ceg_VolumeOfDerivativeActivitiesByContractTypeByContractualSettlementYearLineItems 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 xbrli:stringItemType string No definition available. false 180 Notional amount, monetary 2 invest_DerivativeNotionalAmount invest false na instant No definition available. false false false false false false false false false false false terselabel false 1 true true false false 15500000 15.5 [1] false false false xbrli:monetaryItemType monetary Total monetary amount specified by the derivative(s). Expressed as an absolute value. No authoritative reference available. false 1 Amounts in the table are only intended to provide an indication of the level of derivatives activity and should not be interpreted as a measure of any derivative position or overall economic exposure to market risk. Quantities are expressed as "delta equivalents" on an absolute value basis by contract type by year. Additionally, quantities relate only to derivatives and do not include potentially offsetting quantities associated with physical assets and nonderivative accrual contracts. 1 113 false HundredThousands UnKnown UnKnown true true