Summary of Significant Accounting Policies and Other Matters - Other Deferred Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Public Utility, Property, Plant and Equipment [Line Items]
Prepayments	$ 50	$ 24
Other deferred charges and noncurrent assets	179	105
Depreciation expense, other deferred charges and noncurrent assets and prepayments	21	15	$ 12
Accumulated depreciation, other deferred charges and noncurrent assets and prepayments	58	37
CECONY
Public Utility, Property, Plant and Equipment [Line Items]
Prepayments	49	23
Other deferred charges and noncurrent assets	178	103
Depreciation expense, other deferred charges and noncurrent assets and prepayments	20	14	$ 11
Accumulated depreciation, other deferred charges and noncurrent assets and prepayments	$ 53	$ 33