Environmental Matters - Accrued Liability for Asbestos Suits and Workers' Compensation Proceedings (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Site Contingency [Line Items]
Regulatory Liabilities	$ (4,549)	$ (4,929)
Regulatory assets	6,461	4,987
Asbestos Suits
Site Contingency [Line Items]
Accrued liability	8	8
Regulatory assets	8	8
Workers' Compensation
Site Contingency [Line Items]
Accrued liability	72	78
Regulatory Liabilities	(3)
Regulatory assets		3
CECONY
Site Contingency [Line Items]
Regulatory Liabilities	(4,105)	(4,490)
Regulatory assets	5,989	4,600
CECONY | Asbestos Suits
Site Contingency [Line Items]
Accrued liability	7	7
Regulatory assets	7	7
CECONY | Workers' Compensation
Site Contingency [Line Items]
Accrued liability	68	73
Regulatory Liabilities	$ (3)
Regulatory assets		$ 3