Environmental Matters - Accrued Liability for Asbestos Suits and Workers' Compensation Proceedings (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Site Contingency [Line Items]
Regulatory assets	$ 7,124	$ 8,228
Asbestos Suits
Site Contingency [Line Items]
Accrued liability	8	8
Regulatory assets	8	8
Workers' Compensation
Site Contingency [Line Items]
Accrued liability	88	86
Regulatory assets	13	11
CECONY
Site Contingency [Line Items]
Regulatory assets	6,563	7,603
CECONY | Asbestos Suits
Site Contingency [Line Items]
Accrued liability	7	7
Regulatory assets	7	7
CECONY | Workers' Compensation
Site Contingency [Line Items]
Accrued liability	83	81
Regulatory assets	$ 13	$ 11