Summary of Significant Accounting Policies and Other Matters - Reconciliation of Cash, Temporary Investments and Restricted Cash (Details) $ in Millions	Dec. 31, 2024 USD ($) MWh	Dec. 31, 2023 USD ($)	Mar. 01, 2023 MWh
Cash and Cash Equivalents [Line Items]
Cash and temporary cash investments	$ 1,324	$ 1,189
Restricted cash	9	6
Total cash, temporary cash investments and restricted cash	$ 1,333	1,195
Electric Energy
Cash and Cash Equivalents [Line Items]
Notional amount | MWh	33,303,430
CECONY
Cash and Cash Equivalents [Line Items]
Cash and temporary cash investments	$ 1,254	$ 1,138
CECONY | Electric Energy
Cash and Cash Equivalents [Line Items]
Notional amount | MWh	30,466,200
Clean Energy Businesses | Broken Bow II | Electric Energy
Cash and Cash Equivalents [Line Items]
Notional amount | MWh	75		75