Leases - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Assets under finance leases	$ 3	$ 3	$ 1
Finance leases, accumulated amortization	3	3	5
Right-of-use assets	5	5
CECONY
Lessee, Lease, Description [Line Items]
Assets under finance leases	2	2
Finance leases, accumulated amortization	1	1	$ 3
Right-of-use assets	$ 1	$ 1