Investments (Nuclear Decommissioning Trusts) (Details) - SCE - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Investment Holdings [Line Items]
Unrealized holding gains, net of losses	$ 2,100	$ 1,800
Deferred income taxes related to unrealized gains	515	449
Nuclear decommissioning trusts	$ 4,300	$ 4,100

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