Other Postretirement Benefits - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2014
CECONY | Clean Energy Business and RECO
Defined Benefit Plan Disclosure [Line Items]
Credit to OCI (net of taxes) for unrecognized net losses	$ 2
Debit to OCI (net of taxes) for unrecognized prior service costs	1
CECONY | Clean Energy Businesses
Defined Benefit Plan Disclosure [Line Items]
Credit to OCI (net of taxes) for unrecognized net losses	1
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Decrease in liability for other postretirement benefits	70
Increase in regulatory liabilities	32
Net losses unrecognized to be amortized	4
Prior service cost estimated to be amortized	$ (17)
Health care cost trend rate for net periodic benefit cost, current	6.00%
Health care cost trend rate for net periodic benefit cost	4.50%
Health care cost trend rate for benefit obligations, current	5.80%
Health care cost trend rate for benefit obligations	4.50%
Expected contributions	$ 14
Other Postretirement Benefits | Maximum
Defined Benefit Plan Disclosure [Line Items]
Increase in postretirement benefit obligations (less than)		$ 10
Other Postretirement Benefits | CECONY
Defined Benefit Plan Disclosure [Line Items]
Decrease in liability for other postretirement benefits	67
Increase in regulatory liabilities	32
Net losses unrecognized to be amortized	1
Prior service cost estimated to be amortized	(11)
Expected contributions	$ 10