Environmental Matters - Environmental Remediation Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Environmental Exit Cost [Line Items]
Remediation costs incurred	$ 3	$ 8	$ 8	$ 11
CECONY
Environmental Exit Cost [Line Items]
Remediation costs incurred	$ 3	$ 6	$ 8	$ 8