Summary of Significant Accounting Policies and Other Matters - Reconciliation of Cash, Temporary Investments and Restricted Cash (Details) $ in Millions	Dec. 31, 2023 USD ($) MWh	Dec. 31, 2022 USD ($)
Cash and Cash Equivalents [Line Items]
Cash and temporary cash investments	$ 1,189	$ 1,282
Restricted cash	6	223
Total cash, temporary cash investments and restricted cash	$ 1,195	1,505
Electric Energy
Cash and Cash Equivalents [Line Items]
Notional amount | MWh	34,892,535
Cash Collateral Held For Project Finance Agreements | Clean Energy Businesses
Cash and Cash Equivalents [Line Items]
Restricted cash	$ 6	223
CECONY
Cash and Cash Equivalents [Line Items]
Cash and temporary cash investments	$ 1,138	$ 1,056
CECONY | Electric Energy
Cash and Cash Equivalents [Line Items]
Notional amount | MWh	32,315,225
Clean Energy Businesses | Broken Bow II | Electric Energy
Cash and Cash Equivalents [Line Items]
Notional amount | MWh	75