Fair Value Measurements (Fair Value by Level) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets at fair value
Nuclear decommissioning trusts	$ 4,650	$ 4,562
Southern California Edison
Assets at fair value
Nuclear decommissioning trusts	$ 4,650	$ 4,562
Liabilities at fair value
Percentage of equity investments located in the United States	72.00%	72.00%
Collateralized mortgage obligations and other asset backed securities	$ 31	$ 46
Payables, net, related to investments	176	111
Southern California Edison \| Fair Value, Measurements, Recurring
Assets at fair value
Netting and Collateral	(8)	(15)
Derivative contracts, net	48	87
Money market funds and other	24	18
Nuclear decommissioning trusts	4,826	4,673
Total assets	4,898	4,778
Liabilities at fair value
Netting and Collateral	(8)	(15)
Derivative contracts	0	1
Total liabilities	0	1
Total assets, netting and collateral	0	0
Net assets	4,898	4,777
Southern California Edison \| Fair Value, Measurements, Recurring \| Stocks
Assets at fair value
Nuclear decommissioning trusts	1,753	1,765
Southern California Edison \| Fair Value, Measurements, Recurring \| Fixed Income
Assets at fair value
Nuclear decommissioning trusts	2,651	2,762
Southern California Edison \| Fair Value, Measurements, Recurring \| Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	422	146
Southern California Edison \| Fair Value, Measurements, Recurring \| Level 1
Assets at fair value
Derivative contracts	0	0
Money market funds and other	1	4
Nuclear decommissioning trusts	2,648	2,601
Total assets	2,649	2,605
Liabilities at fair value
Derivative contracts	0	0
Total liabilities	0	0
Net assets	2,649	2,605
Southern California Edison \| Fair Value, Measurements, Recurring \| Level 1 \| Stocks
Assets at fair value
Nuclear decommissioning trusts	1,753	1,765
Southern California Edison \| Fair Value, Measurements, Recurring \| Level 1 \| Fixed Income
Assets at fair value
Nuclear decommissioning trusts	518	738
Southern California Edison \| Fair Value, Measurements, Recurring \| Level 1 \| Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	377	98
Southern California Edison \| Fair Value, Measurements, Recurring \| Level 2
Assets at fair value
Derivative contracts	26	19
Money market funds and other	23	14
Nuclear decommissioning trusts	2,178	2,072
Total assets	2,227	2,105
Liabilities at fair value
Derivative contracts	6	11
Total liabilities	6	11
Net assets	2,221	2,094
Southern California Edison \| Fair Value, Measurements, Recurring \| Level 2 \| Stocks
Assets at fair value
Nuclear decommissioning trusts	0	0
Southern California Edison \| Fair Value, Measurements, Recurring \| Level 2 \| Fixed Income
Assets at fair value
Nuclear decommissioning trusts	2,133	2,024
Southern California Edison \| Fair Value, Measurements, Recurring \| Level 2 \| Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	45	48
Southern California Edison \| Fair Value, Measurements, Recurring \| Level 3
Assets at fair value
Derivative contracts	30	83
Money market funds and other	0	0
Nuclear decommissioning trusts	0	0
Total assets	30	83
Liabilities at fair value
Derivative contracts	2	5
Total liabilities	2	5
Net assets	28	78
Southern California Edison \| Fair Value, Measurements, Recurring \| Level 3 \| Stocks
Assets at fair value
Nuclear decommissioning trusts	0	0
Southern California Edison \| Fair Value, Measurements, Recurring \| Level 3 \| Fixed Income
Assets at fair value
Nuclear decommissioning trusts	0	0
Southern California Edison \| Fair Value, Measurements, Recurring \| Level 3 \| Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	$ 0	$ 0

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This element represents the percentage of equity investments located in United States.

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Interest and dividends receivables and receivables related to pending securities sales and payables related to pending securities purchases as of the balance sheet date.

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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The fair value of investments held in a trust fund to pay for the costs of decontaminating and decommissioning facilities, whether such amount is presented as a separate caption or as a parenthetical disclosure on the balance sheet. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

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Fair value of asset associated with financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, and right to receive cash collateral under master netting arrangements.

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Fair value of asset after deduction of liability.

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Fair value of financial and nonfinancial obligations.

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Fair value portion of other assets.

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