Fair Value Measurements (Fair Value by Level) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Assets at fair value
Nuclear decommissioning trusts	$ 4,344		$ 4,331
Southern California Edison
Assets at fair value
Nuclear decommissioning trusts	$ 4,344	$ 4,290	$ 4,331	$ 4,836	$ 4,896	$ 4,799
Liabilities at fair value
Percentage of equity investments located in the United States (as a percent)	71.00%		70.00%
Collateralized mortgage obligations and other asset backed securities	$ 89		$ 111
Payables, net, related to investments	50		24
Southern California Edison | Fair Value, Measurements, Recurring
Assets at fair value
Derivative contracts	134		163
Other	18		28
Nuclear decommissioning trusts	4,394		4,355
Total assets	4,546		4,546
Liabilities at fair value
Derivative contracts	1,295		1,318
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset			(15)
Total liabilities	1,295		1,318
Net assets (liabilities)	3,251		3,228
Southern California Edison | Fair Value, Measurements, Recurring | Stocks
Assets at fair value
Nuclear decommissioning trusts	1,488		1,460
Southern California Edison | Fair Value, Measurements, Recurring | Fixed income
Assets at fair value
Nuclear decommissioning trusts	2,732		2,723
Southern California Edison | Fair Value, Measurements, Recurring | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	174		172
Southern California Edison | Fair Value, Measurements, Recurring | Level 1
Assets at fair value
Derivative contracts	0		0
Other	18		28
Nuclear decommissioning trusts	2,375		2,498
Total assets	2,393		2,526
Liabilities at fair value
Derivative contracts	0		0
Total liabilities	0		0
Net assets (liabilities)	2,393		2,526
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Stocks
Assets at fair value
Nuclear decommissioning trusts	1,488		1,460
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Fixed income
Assets at fair value
Nuclear decommissioning trusts	830		947
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	57		91
Southern California Edison | Fair Value, Measurements, Recurring | Level 2
Assets at fair value
Derivative contracts	9		0
Other	0		0
Nuclear decommissioning trusts	2,019		1,857
Total assets	2,028		1,857
Liabilities at fair value
Derivative contracts	0		22
Total liabilities	0		22
Net assets (liabilities)	2,028		1,835
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	1,902		1,776
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	117		81
Southern California Edison | Fair Value, Measurements, Recurring | Level 3
Assets at fair value
Derivative contracts	125		163
Other	0		0
Nuclear decommissioning trusts	0		0
Total assets	125		163
Liabilities at fair value
Derivative contracts	1,295		1,311
Total liabilities	1,295		1,311
Net assets (liabilities)	(1,170)		(1,148)
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