Summary of Significant Accounting Policies and Other Matters - Other Deferred Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Public Utility, Property, Plant and Equipment [Line Items]
Prepayments	$ 68	$ 57
Other deferred charges and noncurrent assets	279	254
Depreciation expense, other deferred charges and noncurrent assets and prepayments	47	33	$ 21
Accumulated depreciation, other deferred charges and noncurrent assets and prepayments	92	91
CECONY
Public Utility, Property, Plant and Equipment [Line Items]
Prepayments	65	54
Other deferred charges and noncurrent assets	260	243
Depreciation expense, other deferred charges and noncurrent assets and prepayments	46	32	$ 20
Accumulated depreciation, other deferred charges and noncurrent assets and prepayments	$ 89	$ 85