Summary of Significant Accounting Policies and Other Matters - Other Deferred Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Public Utility, Property, Plant and Equipment [Line Items]
Prepayments	$ 57	$ 50
Other deferred charges and noncurrent assets	254	179
Depreciation expense, other deferred charges and noncurrent assets and prepayments	33	21	$ 15
Accumulated depreciation, other deferred charges and noncurrent assets and prepayments	91	58
CECONY
Public Utility, Property, Plant and Equipment [Line Items]
Prepayments	54	49
Other deferred charges and noncurrent assets	243	178
Depreciation expense, other deferred charges and noncurrent assets and prepayments	32	20	$ 14
Accumulated depreciation, other deferred charges and noncurrent assets and prepayments	$ 85	$ 53