Regulatory Matters - Regulatory Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	$ 5,328.0	$ 6,027.0
Regulatory liabilities—current	145.0	374.0
Total Regulatory Liabilities	5,473.0	6,401.0
Regulatory assets	4,607.0	3,974.0
Future income tax
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	1,535.0	1,753.0
Allowance for cost of removal less salvage
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	1,456.0	1,315.0
Unrecognized pension and other postretirement costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	943.0	1,638.0
Pension and other postretirement benefit deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	284.0	144.0
Net unbilled revenue deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	278.0	204.0
2022 and 2023 late payment charge deferral
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	167.0	127.0
System benefit charge carrying charge
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	92.0	73.0
Deferred derivative gains - long term
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	49.0	145.0
Net proceeds from sale of property
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	48.0	69.0
Settlement of prudence proceeding
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	11.0	10.0
Other
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	465.0	549.0
Deferred derivative gains - short term
Regulatory Liabilities [Line Items]
Regulatory liabilities—current	74.0	311.0
Refundable energy costs
Regulatory Liabilities [Line Items]
Regulatory liabilities—current	71.0	34.0
Revenue decoupling mechanism
Regulatory Liabilities [Line Items]
Regulatory liabilities—current	0.0	29.0
CECONY
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	4,818.0	5,481.0
Regulatory liabilities—current	107.0	308.0
Regulatory assets	4,314.0	3,669.0
CECONY | Arrears Relief Program Deferral [Member]
Regulatory Liabilities [Line Items]
Regulatory assets	398.6	93.5
CECONY | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	4,818.0	5,481.0
Regulatory liabilities—current	107.0	308.0
Total Regulatory Liabilities	4,925.0	5,789.0
Regulatory assets	4,314.0	3,669.0
CECONY | Future income tax | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	1,404.0	1,616.0
CECONY | Allowance for cost of removal less salvage | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	1,266.0	1,137.0
CECONY | Unrecognized pension and other postretirement costs | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	867.0	1,536.0
CECONY | Pension and other postretirement benefit deferrals | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	233.0	98.0
CECONY | Net unbilled revenue deferrals | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	278.0	204.0
CECONY | 2022 and 2023 late payment charge deferral | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	161.0	123.0
CECONY | System benefit charge carrying charge | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	88.0	69.0
CECONY | Deferred derivative gains - long term | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	49.0	130.0
CECONY | Net proceeds from sale of property | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	47.0	69.0
CECONY | Settlement of prudence proceeding | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	11.0	10.0
CECONY | Other | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	414.0	489.0
CECONY | Deferred derivative gains - short term | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities—current	71.0	287.0
CECONY | Refundable energy costs | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities—current	36.0	0.0
CECONY | Revenue decoupling mechanism | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities—current	0.0	21.0
O&R | Arrears Relief Program Deferral [Member]
Regulatory Liabilities [Line Items]
Regulatory assets	$ 2.1	$ 2.6