Leases - Other Related Information (Details)	Mar. 31, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Weighted Average Remaining Lease Term, Operating leases	18 years 10 months 24 days	19 years 1 month 6 days
Weighted Average Remaining Lease Term, Finance leases	7 years 3 months 18 days	7 years 3 months 18 days
Weighted Average Discount Rate, Operating leases	4.30%	4.30%
Weighted Average Discount Rate, Finance leases	1.80%	1.80%
CECONY
Lessee, Lease, Description [Line Items]
Weighted Average Remaining Lease Term, Operating leases	12 years 9 months 18 days	13 years
Weighted Average Remaining Lease Term, Finance leases	3 years 9 months 18 days	4 years
Weighted Average Discount Rate, Operating leases	3.60%	3.60%
Weighted Average Discount Rate, Finance leases	1.30%	1.30%