Other Material Contingencies - Total Guarantees (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Guarantor Obligations [Line Items]
Total guarantees, by type and term	$ 2,370	$ 2,856
Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	1,048
Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	736
Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	458
Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	128
0 – 3 years
Guarantor Obligations [Line Items]
Total guarantees, by type and term	1,605
0 – 3 years | Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	435
0 – 3 years | Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	603
0 – 3 years | Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	439
0 – 3 years | Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	128
4 – 10 years
Guarantor Obligations [Line Items]
Total guarantees, by type and term	648
4 – 10 years | Con Edison Transmission
Guarantor Obligations [Line Items]
Total guarantees, by type and term	613
4 – 10 years | Energy transactions
Guarantor Obligations [Line Items]
Total guarantees, by type and term	35
4 – 10 years | Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	0
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	117
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	98
Greater than 10 years | Renewable electric production projects
Guarantor Obligations [Line Items]
Total guarantees, by type and term	19
Greater than 10 years | Other
Guarantor Obligations [Line Items]
Total guarantees, by type and term	$ 0