Leases - Other Related Information (Details)	Sep. 30, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Weighted Average Remaining Lease Term, Operating leases	19 years	19 years 9 months 18 days
Weighted Average Remaining Lease Term, Finance leases	7 years 4 months 24 days	12 years 2 months 12 days
Weighted Average Discount Rate, Operating leases	4.40%	4.30%
Weighted Average Discount Rate, Finance leases	1.80%	3.50%
CECONY
Lessee, Lease, Description [Line Items]
Weighted Average Remaining Lease Term, Operating leases	13 years 3 months 18 days	14 years
Weighted Average Remaining Lease Term, Finance leases	4 years 2 months 12 days	2 years 4 months 24 days
Weighted Average Discount Rate, Operating leases	3.60%	3.60%
Weighted Average Discount Rate, Finance leases	1.30%	4.10%