Derivative Instruments and Hedging Activities - Additional Information (Detail) $ in Millions	3 Months Ended
Mar. 31, 2016 USD ($)
Investment Holdings [Line Items]
Energy supply and hedging activities credit exposure total	$ 209
Makeup of net credit exposure with commodity exchange brokers	112
Makeup of net credit exposure independent system operators	63
Makeup of net credit exposure with investment-grade counterparties	27
Makeup of net credit exposure non-investment grade/non-rated counterparties	7
CECONY
Investment Holdings [Line Items]
Energy supply and hedging activities credit exposure total	$ 17

Credit Exposure Independent System Operators

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- Definition

Credit exposure nonrated counterparties

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- Definition

Maximum Potential Future Exposure On Credit Risk Derivatives With Commodity Exchange Brokers

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- Definition

Maximum Potential Future Exposure On Credit Risk Derivatives With Investment Grade Counterparties

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- Definition

Maximum potential amount of future undiscounted payments that could be required under the credit derivative, before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4K
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5708775-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Credit Derivative
-URI http://asc.fasb.org/extlink&oid=6854095

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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.

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