Other Material Contingencies - Guarantees (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Guarantor Obligations [Line Items]
Total guarantees, by type and term	$ 1,967	$ 2,439
Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	672
Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	712
Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	513
Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	70
0 – 3 years
Guarantor Obligations [Line Items]
Total guarantees, by type and term	1,227
0 – 3 years | Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	535
0 – 3 years | Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	494
0 – 3 years | Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	128
0 – 3 years | Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	70
4 – 10 years
Guarantor Obligations [Line Items]
Total guarantees, by type and term	167
4 – 10 years | Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	137
4 – 10 years | Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	21
4 – 10 years | Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	9
4 – 10 years | Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	0
Greater than 10 years
Guarantor Obligations [Line Items]
Total guarantees, by type and term	573
Greater than 10 years | Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	0
Greater than 10 years | Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	197
Greater than 10 years | Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	376
Greater than 10 years | Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	$ 0