Other Material Contingencies - Total Guarantees (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Guarantor Obligations [Line Items]
Total guarantees, by type and term	$ 1,831	$ 2,439
Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	573
Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	679
Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	510
Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	69
0 – 3 years
Guarantor Obligations [Line Items]
Total guarantees, by type and term	945
0 – 3 years | Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	387
0 – 3 years | Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	419
0 – 3 years | Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	70
0 – 3 years | Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	69
4 – 10 years
Guarantor Obligations [Line Items]
Total guarantees, by type and term	246
4 – 10 years | Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	186
4 – 10 years | Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	51
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
10 years
Guarantor Obligations [Line Items]
Total guarantees, by type and term	640
10 years | Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	0
10 years | Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	209
10 years | Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	431
10 years | Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	$ 0