Summary of Significant Accounting Policies (Emission Allowances and Energy Credits) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
LCFS net sales proceeds
Significant Accounting Policies [Line Items]
Regulatory liabilities	$ 176	$ 184
SCE
Significant Accounting Policies [Line Items]
Regulatory liabilities	9,158	9,357
SCE | Other current assets
Significant Accounting Policies [Line Items]
GHG allowances	78	50
SCE | Other current liabilities
Significant Accounting Policies [Line Items]
GHG emission obligations	$ 64	$ 50