Leases - Lease Cost and Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 22	$ 22	$ 44	$ 43
Operating lease cash flows	8	8	17	16
CECONY | Subsidiaries
Lessee, Lease, Description [Line Items]
Operating lease cost	17	16	33	33
Operating lease cash flows	$ 4	$ 4	$ 8	$ 9