Other Postretirement Benefits - Additional Information (Details) - Other Postretirement Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Increase (decrease) in liability for other postretirement benefits	$ (21)	$ 102
Increase (decrease) in regulatory liabilities	$ 36
Health care cost trend rate for net periodic benefit cost, current	5.20%	5.40%	5.60%
Health care cost trend rate for net periodic benefit cost	4.50%
Health care cost trend rate for benefit obligations, current	7.04%	5.20%	5.40%
Health care cost trend rate for benefit obligations	4.50%
Expected contributions	$ 6
Clean Energy Businesses, Con Edison Transmission and RECO
Defined Benefit Plan Disclosure [Line Items]
Credit to OCI (net of taxes) for unrecognized net losses	2
CECONY
Defined Benefit Plan Disclosure [Line Items]
Increase (decrease) in liability for other postretirement benefits	(13)	$ 128
Increase (decrease) in regulatory liabilities	33
Expected contributions	$ 3