Other Postretirement Benefits - Additional Information (Detail) (Other Postretirement Benefits [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Schedule Of Other Postretirement Benefits [Line Items]
Expected contributions	$ 9
CECONY [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Expected contributions	$ 9

The employer's best estimate, as soon as it can be reasonably determined, of contributions expected to be paid to the plan in the current remaining fiscal period. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions.

No definition available.

Name:	us-gaap_DefinedBenefitPlanEstimatedFutureEmployerContributionsInCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant