Summary of Significant Accounting Policies - Changes in Accumulated Other Comprehensive Income by Component (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Definition Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Tax Amounts reclassified from accumulated OCI related to pension plan liabilities, tax	$ 1

Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Tax

No definition available.

Name:	ed_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansTax
Namespace Prefix:	ed_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant