Pension Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2014
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions	$ 564
Pension Benefits [Member] \| CECONY [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions	524
Contributions	200
Non-qualified Supplemental Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions	$ 13

Amount of employer's best estimate of contributions expected to be paid to the plan in the current remaining fiscal period.

No definition available.

Name:	us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration