Environmental Matters - Accrued Liability (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Site Contingency [Line Items]
Regulatory assets	$ 4,875	$ 4,987
Asbestos Suits
Site Contingency [Line Items]
Accrued liability	8	8
Regulatory assets	8	8
Workers’ Compensation
Site Contingency [Line Items]
Accrued liability	77	78
Regulatory assets	2	3
CECONY
Site Contingency [Line Items]
Regulatory assets	4,490	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	72	73
Regulatory assets	$ 2	$ 3