Leases - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
Lessee, Lease, Description [Line Items]
Assets under finance leases	$ 3
Finance leases, accumulated amortization	3
Right-of-use assets	16
CECONY
Lessee, Lease, Description [Line Items]
Assets under finance leases	2
Finance leases, accumulated amortization	1
Right-of-use assets	$ 1