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Financial Information by Business Segment - Financial Data for Business Segments (Parenthetical) (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Segment Reporting Information [Line Items]      
Income taxes on non-operating income $ (21)ed_IncomeTaxBenefitApplicableToNonOperatingIncome $ (28)ed_IncomeTaxBenefitApplicableToNonOperatingIncome $ 6ed_IncomeTaxBenefitApplicableToNonOperatingIncome
CECONY [Member]      
Segment Reporting Information [Line Items]      
Income taxes on non-operating income $ (7)ed_IncomeTaxBenefitApplicableToNonOperatingIncome
/ dei_LegalEntityAxis
= ed_CeconyMember		 $ (11)ed_IncomeTaxBenefitApplicableToNonOperatingIncome
/ dei_LegalEntityAxis
= ed_CeconyMember		 $ 15ed_IncomeTaxBenefitApplicableToNonOperatingIncome
/ dei_LegalEntityAxis
= ed_CeconyMember