Taxes (Details 3) $ in Millions	Dec. 31, 2016 USD ($)
State
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	$ 7,062
State | 2017-2021
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	166
State | 2022-2026
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	1,327
State | 2027-2031
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	2,817
State | 2032-2036
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	2,752
Local
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	2,998
Local | 2017-2021
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	2,998
Local | 2022-2026
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	0
Local | 2027-2031
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	0
Local | 2032-2036
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	0
FES | State
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	1,584
FES | State | 2017-2021
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	2
FES | State | 2022-2026
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	0
FES | State | 2027-2031
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	410
FES | State | 2032-2036
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	1,172
FES | Local
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	1,795
FES | Local | 2017-2021
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	1,795
FES | Local | 2022-2026
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	0
FES | Local | 2027-2031
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	0
FES | Local | 2032-2036
Pre-tax net operating loss expiration period
Pre-tax net operating loss carryforwards for state and local income tax purposes	$ 0