Derivative Instruments and Hedging Activities - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Investment Holdings [Line Items]
Energy supply and hedging activities credit exposure total	$ 62
Makeup of net credit exposure with commodity exchange brokers	25
Makeup of net credit exposure with investment-grade counterparties	17
Makeup of net credit exposure independent system operators	9
Makeup of net credit exposure non-investment grade/non-rated counterparties	11
Derivative liabilities	117	$ 183
Interest Rate Swap
Investment Holdings [Line Items]
Derivative liabilities	1	$ 0
CECONY
Investment Holdings [Line Items]
Energy supply and hedging activities credit exposure total	20
Makeup of net credit exposure with commodity exchange brokers	14
Makeup of net credit exposure with investment-grade counterparties	$ 6
Clean Energy Businesses \| Coram \| Interest Rate Swap
Investment Holdings [Line Items]
Derivative, fixed interest rate	2.0855%
Derivative liabilities	$ 1

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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.

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-Publisher FASB
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Fixed interest rate related to the interest rate derivative.

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