Derivative Instruments and Hedging Activities - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Investment Holdings [Line Items]
Energy supply and hedging activities credit exposure total	$ 217
Makeup of net credit exposure with investment-grade counterparties	47
Makeup of net credit exposure independent system operators	103
Makeup of net credit exposure with commodity exchange brokers	27
Makeup of net credit exposure non-investment grade/non-rated counterparties	40
CECONY
Investment Holdings [Line Items]
Energy supply and hedging activities credit exposure total	16
Makeup of net credit exposure with commodity exchange brokers	$ 16