Summary of Significant Accounting Policies (Emission Allowances and Energy Credits) (Details) - SCE - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Significant Accounting Policies [Line Items]
Regulatory liabilities	$ 9,357	$ 9,861
LCFS net sales proceeds
Significant Accounting Policies [Line Items]
Regulatory liabilities	184	103
Other Current Assets
Significant Accounting Policies [Line Items]
GHG allowances	50	38
Other Current Liabilities
Significant Accounting Policies [Line Items]
GHG emission obligations	$ 50	$ 30