Leases - Lease Cost and Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 17	$ 22	$ 53	$ 66
Operating lease cash flows	6	11	17	28
CECONY | Subsidiaries
Lessee, Lease, Description [Line Items]
Operating lease cost	17	17	49	50
Operating lease cash flows	$ 6	$ 5	$ 14	$ 13