Commitments and Contingencies (Third-Party Power Purchase Agreements) (Details) - Southern California Edison - Commitments meeting critical contract provisions $ in Millions	Sep. 30, 2017 USD ($)
Unrecorded Unconditional Purchase Obligation [Line Items]
Estimated commitments in two years	$ 27
Estimated commitments in three years	72
Estimated commitments in four years	62
Estimated commitments in five years	20
Estimated commitments after five years	$ 1,200