Other Postretirement Benefits - Additional Information (Details) - Other Postretirement Benefits $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Decrease in liability for other postretirement benefits	$ 43
Increase in regulatory liabilities	11
Net losses unrecognized to be amortized	8
Prior service cost estimated to be amortized	$ (6)
Health care cost trend rate for net periodic benefit cost, current	5.80%
Health care cost trend rate for net periodic benefit cost	4.50%
Health care cost trend rate for benefit obligations, current	5.60%
Health care cost trend rate for benefit obligations	4.50%
Expected contributions	$ 7
Clean Energy Businesses, Con Edison Transmission and RECO
Defined Benefit Plan Disclosure [Line Items]
Debit to OCI (net of taxes) for unrecognized net losses	3
Change to OCI (net of taxes) for unrecognized prior service costs	0
CECONY
Defined Benefit Plan Disclosure [Line Items]
Decrease in liability for other postretirement benefits	64
Increase in regulatory liabilities	32
Net losses unrecognized to be amortized	1
Prior service cost estimated to be amortized	$ (2)