Commitments and Contingencies (Montecito Mudslides) (Details) $ in Millions	Mar. 31, 2018 USD ($)	Jan. 31, 2018 structure fatality
Montecito mudslides
Loss Contingencies [Line Items]
Structures destroyed | structure		135
Structures damaged | structure		324
Fatalities | fatality		21
Additional fatalities | fatality		2
Southern California Edison
Loss Contingencies [Line Items]
Other general liability insurance coverage | $	$ 450