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Derivative Instruments and Hedging Activities - Additional Information (Details) $ in Millions | 9 Months Ended
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Sep. 30, 2019 USD ($)
Investment Holdings [Line Items] |
Energy supply and hedging activities credit exposure total | $ 154
Makeup of net credit exposure non-investment grade/non-rated counterparties | 50
Makeup of net credit exposure independent system operators | 58
Makeup of net credit exposure with investment-grade counterparties | 35
Makeup of net credit exposure with commodity exchange brokers | 11
CECONY |
Investment Holdings [Line Items] |
Energy supply and hedging activities credit exposure total | 6
Makeup of net credit exposure with commodity exchange brokers | $ 6

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