The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph b

-URI http://asc.fasb.org/extlink&oid=52262685&loc=d3e5728-111685

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 6

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=52262685&loc=d3e5747-111685

Name:	us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Variable Interest Entities - Additional Information (Detail) $ in Millions	Jun. 30, 2015 USD ($)	Dec. 31, 2014 entity
Cogen Technologies Linden Venture, LP
Variable Interest Entity [Line Items]
Maximum exposure to loss	$ 177
Brooklyn Navy Yard Cogeneration Partners, LP
Variable Interest Entity [Line Items]
Maximum exposure to loss	54
Indeck Energy Services of Corinth, Inc
Variable Interest Entity [Line Items]
Maximum exposure to loss	$ 28
CECONY
Variable Interest Entity [Line Items]
Number of potential VIEs, long-term electricity purchase agreements \| entity		3