Regulatory Matters - Schedule of Regulatory Assets Not Earning a Return (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Regulatory Assets [Line Items]
Regulatory assets not earning return	$ 2,272	$ 2,281
Subsidiaries | CECONY
Regulatory Assets [Line Items]
Regulatory assets not earning return	2,124	2,137
Environmental investigation and remediation costs
Regulatory Assets [Line Items]
Regulatory assets not earning return	1,074	1,072
Environmental investigation and remediation costs | Subsidiaries | CECONY
Regulatory Assets [Line Items]
Regulatory assets not earning return	983	980
Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets not earning return	642	621
Revenue taxes | Subsidiaries | CECONY
Regulatory Assets [Line Items]
Regulatory assets not earning return	615	595
UB deferral for uncollectible accounts receivable
Regulatory Assets [Line Items]
Regulatory assets not earning return	395	427
UB deferral for uncollectible accounts receivable | Subsidiaries | CECONY
Regulatory Assets [Line Items]
Regulatory assets not earning return	392	426
Deferred derivative losses - short term
Regulatory Assets [Line Items]
Regulatory assets not earning return	75	97
Deferred derivative losses - short term | Subsidiaries | CECONY
Regulatory Assets [Line Items]
Regulatory assets not earning return	70	90
Deferred derivative losses - long term
Regulatory Assets [Line Items]
Regulatory assets not earning return	23	18
Deferred derivative losses - long term | Subsidiaries | CECONY
Regulatory Assets [Line Items]
Regulatory assets not earning return	21	15
Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets not earning return	7	4
Unrecognized pension and other postretirement costs | Subsidiaries | CECONY
Regulatory Assets [Line Items]
Regulatory assets not earning return	0	0
Other
Regulatory Assets [Line Items]
Regulatory assets not earning return	56	42
Other | Subsidiaries | CECONY
Regulatory Assets [Line Items]
Regulatory assets not earning return	$ 43	$ 31