Regulatory Matters - Regulatory Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	$ 4,946	$ 5,444
Regulatory liabilities – current	123	102
Total Regulatory Liabilities	5,069	5,546
Allowance for cost of removal less salvage
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	1,597	1,527
Future income tax
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	1,146	1,224
Unrecognized pension and other postretirement costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	736	1,054
Pension and other postretirement benefit deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	373	368
Net unbilled revenue deferrals
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	296	436
Late payment charge deferral
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	223	231
System benefit charge carrying charge
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	103	115
Deferred derivative gains - long term
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	16	8
Settlement of prudence proceeding
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	9	10
Other
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	447	471
Deferred derivative gains - short term
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	22	25
Refundable energy costs
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	84	59
Revenue decoupling mechanism
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	17	18
CECONY
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	4,466	4,940
Regulatory liabilities – current	73	40
CECONY | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	4,466	4,940
Regulatory liabilities – current	73	40
Total Regulatory Liabilities	4,539	4,980
CECONY | Allowance for cost of removal less salvage | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	1,383	1,322
CECONY | Future income tax | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	1,039	1,112
CECONY | Unrecognized pension and other postretirement costs | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	684	984
CECONY | Pension and other postretirement benefit deferrals | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	324	304
CECONY | Net unbilled revenue deferrals | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	296	436
CECONY | Late payment charge deferral | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	219	224
CECONY | System benefit charge carrying charge | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	96	110
CECONY | Deferred derivative gains - long term | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	12	6
CECONY | Settlement of prudence proceeding | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	9	10
CECONY | Other | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – noncurrent	404	432
CECONY | Deferred derivative gains - short term | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	18	22
CECONY | Refundable energy costs | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	55	18
CECONY | Revenue decoupling mechanism | Subsidiaries
Regulatory Liabilities [Line Items]
Regulatory liabilities – current	$ 0	$ 0