Variable Interest Entities - Additional Information (Detail) - CECONY	12 Months Ended
Dec. 31, 2015 entity counterparty
Variable Interest Entity [Line Items]
Number of potential VIEs, long-term electricity purchase agreements \| entity	2
Number of counterparties \| counterparty	2

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_VariableInterestEntityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration