Leases - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Assets under finance leases	$ 1
Finance leases, accumulated amortization	5
Right-of-use asset obtained in exchange for operating lease liability	39
CECONY
Lessee, Lease, Description [Line Items]
Finance leases, accumulated amortization	3
Right-of-use asset obtained in exchange for operating lease liability	$ 4
Minimum
Lessee, Lease, Description [Line Items]
Lease, term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lease, term	40 years
Lease, renewal term	5 years