Environmental Matters - Accrued Liabilities and Regulatory Assets (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Site Contingency [Line Items]
Accrued liabilities	$ 770	$ 779
Regulatory assets	4,334	4,370
Manufactured gas plant sites
Site Contingency [Line Items]
Accrued liabilities	681	689
Other Superfund Sites
Site Contingency [Line Items]
Accrued liabilities	89	90
Superfund Sites
Site Contingency [Line Items]
Accrued liabilities	770	779
Regulatory assets	787	810
CECONY
Site Contingency [Line Items]
Accrued liabilities	686	693
Regulatory assets	3,976	3,987
CECONY | Manufactured gas plant sites
Site Contingency [Line Items]
Accrued liabilities	598	603
CECONY | Other Superfund Sites
Site Contingency [Line Items]
Accrued liabilities	88	90
CECONY | Superfund Sites
Site Contingency [Line Items]
Accrued liabilities	686	693
Regulatory assets	$ 696	$ 716