Fair Value Measurements (Fair Value by Level) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets at fair value
Nuclear decommissioning trusts		$ 4,331	$ 4,799
Liabilities at fair value
Money market funds		37	35
Level 1
Liabilities at fair value
Money market funds		29	30
Southern California Edison
Assets at fair value
Nuclear decommissioning trusts		$ 4,331	$ 4,799	$ 4,494	$ 4,048
Liabilities at fair value
Percentage of equity investments located in the United States (as a percent)		70.00%	73.00%
Collateralized mortgage obligations and other asset backed securities		$ 111	$ 49
Receivables (payables) net related to investments		(24)	(57)
Money market funds		8	5
Southern California Edison | Stocks
Assets at fair value
Nuclear decommissioning trusts		1,460	2,031
Southern California Edison | Fair Value, Measurements, Recurring | Level 1
Assets at fair value
Derivative contracts		0	0
Other		28	33
Nuclear decommissioning trusts	[1]	2,498	3,340
Total assets		2,526	3,373
Liabilities at fair value
Derivative contracts		0	0
Total liabilities		0	0
Net assets (liabilities)		2,526	3,373
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Stocks
Assets at fair value
Nuclear decommissioning trusts	[2]	1,460	2,031
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Fixed Income
Assets at fair value
Nuclear decommissioning trusts	[3]	947	703
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts		91	606
Southern California Edison | Fair Value, Measurements, Recurring | Level 2
Assets at fair value
Derivative contracts		0	0
Other		0	0
Nuclear decommissioning trusts	[1]	1,857	1,516
Total assets		1,857	1,516
Liabilities at fair value
Derivative contracts		22	86
Total liabilities		22	86
Net assets (liabilities)		1,835	1,430
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Stocks
Assets at fair value
Nuclear decommissioning trusts	[2]	0	0
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Fixed Income
Assets at fair value
Nuclear decommissioning trusts	[3]	1,776	1,350
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts		81	166
Southern California Edison | Fair Value, Measurements, Recurring | Level 3
Assets at fair value
Derivative contracts		163	321
Other		0	0
Nuclear decommissioning trusts	[1]	0	0
Total assets		163	321
Liabilities at fair value
Derivative contracts		1,311	1,223
Total liabilities		1,311	1,223
Net assets (liabilities)		(1,148)	(902)
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Stocks
Assets at fair value
Nuclear decommissioning trusts	[2]	0	0
Southern California Edison | Fair Value, Measurements, Recurring | Level 3 | Fixed Income
Assets at fair value
Nuclear decommissioning trusts	[3]	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
Southern California Edison | Fair Value, Measurements, Recurring | Gross amounts offset in consolidated balance sheets
Assets at fair value
Derivative contracts	[4]	0	0
Other	[4]	0	0
Nuclear decommissioning trusts	[1],[4]	0	0
Total assets	[4]	0	0
Liabilities at fair value
Derivative contracts	[4]	(15)	(61)
Total liabilities	[4]	(15)	(61)
Net assets (liabilities)	[4]	15	61
Southern California Edison | Fair Value, Measurements, Recurring | Gross amounts offset in consolidated balance sheets | Stocks
Assets at fair value
Nuclear decommissioning trusts	[2],[4]	0	0
Southern California Edison | Fair Value, Measurements, Recurring | Gross amounts offset in consolidated balance sheets | Fixed Income
Assets at fair value
Nuclear decommissioning trusts	[3],[4]	0	0
Southern California Edison | Fair Value, Measurements, Recurring | Gross amounts offset in consolidated balance sheets | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	[4]	0	0
Southern California Edison | Fair Value, Measurements, Recurring | Total
Assets at fair value
Derivative contracts		163	321
Other		28	33
Nuclear decommissioning trusts	[1]	4,355	4,856
Total assets		4,546	5,210
Liabilities at fair value
Derivative contracts		1,318	1,248
Total liabilities		1,318	1,248
Net assets (liabilities)		3,228	3,962
Southern California Edison | Fair Value, Measurements, Recurring | Total | Stocks
Assets at fair value
Nuclear decommissioning trusts	[2]	1,460	2,031
Southern California Edison | Fair Value, Measurements, Recurring | Total | Fixed Income
Assets at fair value
Nuclear decommissioning trusts	[3]	2,723	2,053
Southern California Edison | Fair Value, Measurements, Recurring | Total | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts		$ 172	$ 772

[1] Excludes net payables of $24 million and $57 million at December 31, 2015 and 2014, which consist of interest and dividend receivables as well as receivables and payables related to SCE's pending securities sales and purchases.

[2] Approximately 70% and 73% of SCE's equity investments were located in the United States at December 31, 2015 and 2014, respectively.

[3] Includes corporate bonds, which were diversified and included collateralized mortgage obligations and other asset backed securities of $111 million and $49 million at December 31, 2015 and 2014, respectively.

[4] Represents the netting of assets and liabilities under master netting agreements and cash collateral across the levels of the fair value hierarchy. Netting among positions classified within the same level is included in that level.