2.2.0.7 true Fair Value Measurements (Narrative) (Details) (USD $) 41201 - Disclosure - Fair Value Measurements (Narrative) (Details) true false In Millions false false 1 USD true false false false Fair Value Gain Loss Included In Non Utility Revenue [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueGainLossIncludedInNonUtilityRevenueMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 2 USD true false false false Fair Value Gain Loss Included In Non Utility Revenue [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueGainLossIncludedInNonUtilityRevenueMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 3 USD true false false false Fair Value Gain Loss Included In Non Utility Revenue [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueGainLossIncludedInNonUtilityRevenueMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 4 USD true false false false Fair Value Gain Loss Included In Non Utility Revenue [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueGainLossIncludedInNonUtilityRevenueMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ 1 Fair Value Gain Loss Included In Non Utility Revenue [Member] 0 na true na na No definition available. false true false false false false false false false false false http://www.coned.com/taxonomy/role/disclosurefairvaluemeasurementsnarrativedetails 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 4 false false false false 0 0 false false false false 1 USD true false false false Fair Value Gain Loss Included In Non Utility Revenue [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueGainLossIncludedInNonUtilityRevenueMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 2 USD true false false false Fair Value Gain Loss Included In Non Utility Revenue [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueGainLossIncludedInNonUtilityRevenueMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 3 USD true false false false Fair Value Gain Loss Included In Non Utility Revenue [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueGainLossIncludedInNonUtilityRevenueMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 4 USD true false false false Fair Value Gain Loss Included In Non Utility Revenue [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueGainLossIncludedInNonUtilityRevenueMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 2 Competitive energy businesses, realized and unrealized gains and losses on level 3 commodity derivative assets and liabilities, included in non-utility revenues and purchased power costs 2 us-gaap_FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInOtherIncome us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 true true false false 14000000 14 false false false 2 true true false false -68000000 -68 false false false 3 true true false false 47000000 47 false false false 4 true true false false -121000000 -121 false false false xbrli:monetaryItemType monetary This item represents the amount of the total realized and unrealized gains or losses for the period which are included in the statement of income (or changes in net assets) in other income; the fair value of which assets was or is measured on a recurring basis using significant unobservable inputs (Level 3). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 32 -Subparagraph c(1) false 4 Fair Value Gain Loss Included In Purchased Power Costs [Member] 0 na true na na No definition available. false true false false false false false false false false false http://www.coned.com/taxonomy/role/disclosurefairvaluemeasurementsnarrativedetails 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 4 false false false false 0 0 false false false false 5 USD true false false false Fair Value Gain Loss Included In Purchased Power Costs [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueGainLossIncludedInPurchasedPowerCostsMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 6 USD true false false false Fair Value Gain Loss Included In Purchased Power Costs [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueGainLossIncludedInPurchasedPowerCostsMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 7 USD true false false false Fair Value Gain Loss Included In Purchased Power Costs [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueGainLossIncludedInPurchasedPowerCostsMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 5 Competitive energy businesses, realized and unrealized gains and losses on level 3 commodity derivative assets and liabilities, included in non-utility revenues and purchased power costs 2 us-gaap_FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInOtherIncome 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 -33000000 -33 false false false 2 false false false false 0 0 false false false 3 false true false false -73000000 -73 false false false 4 false true false false -2000000 -2 false false false xbrli:monetaryItemType monetary This item represents the amount of the total realized and unrealized gains or losses for the period which are included in the statement of income (or changes in net assets) in other income; the fair value of which assets was or is measured on a recurring basis using significant unobservable inputs (Level 3). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 32 -Subparagraph c(1) false 7 Fair Value Change Included In Non Utility Revenue [Member] 0 na true na na No definition available. false true false false false false false false false false false http://www.coned.com/taxonomy/role/disclosurefairvaluemeasurementsnarrativedetails 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 4 false false false false 0 0 false false false false 8 USD true false false false Fair Value Change Included In Non Utility Revenue [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueChangeIncludedInNonUtilityRevenueMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 9 USD true false false false Fair Value Change Included In Non Utility Revenue [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueChangeIncludedInNonUtilityRevenueMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 10 USD true false false false Fair Value Change Included In Non Utility Revenue [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueChangeIncludedInNonUtilityRevenueMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 11 USD true false false false Fair Value Change Included In Non Utility Revenue [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueChangeIncludedInNonUtilityRevenueMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 9 Change in unrealized gain (loss) on fair value hedging instruments 2 us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments us-gaap true debit duration No definition available. false false false false false false false false false false false label false 1 false true false false -3000000 -3 false false false 2 false true false false -15000000 -15 false false false 3 false true false false -2000000 -2 false false false 4 false true false false -15000000 -15 false false false xbrli:monetaryItemType monetary Amount of the increase or decrease in fair value during the period of derivative or nonderivative instruments designated as fair value hedging instruments. Recognized in earnings and offsets the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 45 -Subparagraph a(1) false 10 Fair Value Change Included In Purchased Power Costs [Member] 0 na true na na No definition available. false true false false false false false false false false false http://www.coned.com/taxonomy/role/disclosurefairvaluemeasurementsnarrativedetails 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 4 false false false false 0 0 false false false false 12 USD true false false false Fair Value Change Included In Purchased Power Costs [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueChangeIncludedInPurchasedPowerCostsMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 13 USD true false false false Fair Value Change Included In Purchased Power Costs [Member] us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis xbrldi http://xbrl.org/2006/xbrldi ed_FairValueChangeIncludedInPurchasedPowerCostsMember us-gaap_FairValueEstimateNotPracticableDisclosureItemsAxis explicitMember Unit12 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 12 Change in unrealized gain (loss) on fair value hedging instruments 2 us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments us-gaap true debit duration No definition available. false false false false false false false false false false false label false 1 true true false false -22000000 -22 false false false 2 false false false false 0 0 false false false 3 true true false false -29000000 -29 false false false 4 false false false false 0 0 false false false xbrli:monetaryItemType monetary Amount of the increase or decrease in fair value during the period of derivative or nonderivative instruments designated as fair value hedging instruments. Recognized in earnings and offsets the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 45 -Subparagraph a(1) false 4 8 false Millions UnKnown UnKnown false true