Leases - Lease Cost and Cash Flows (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 83
Operating lease cash flows	75
CECONY
Lessee, Lease, Description [Line Items]
Operating lease cost	64
Operating lease cash flows	$ 60