Fair Value Measurements (Fair Value by Level) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Assets at fair value
Nuclear decommissioning trusts	$ 4,388		$ 4,799
Liabilities at fair value
Money market funds	35		35
Southern California Edison
Assets at fair value
Nuclear decommissioning trusts	$ 4,388	$ 4,836	$ 4,799	$ 4,741	$ 4,740	$ 4,494
Liabilities at fair value
Percentage of equity investments located in the United States (as a percent)	68.00%		73.00%
Collateralized mortgage obligations and other asset backed securities	$ 149		$ 49
Payables, net, related to investments	31		57
Money market funds	5		5
Southern California Edison | Fair Value, Measurements, Recurring
Liabilities at fair value
Liability offset	(35)		(61)
Asset offset	35		61
Southern California Edison | Fair Value, Measurements, Recurring | Level 1
Assets at fair value
Derivative contracts	0		0
Other	25		33
Nuclear decommissioning trusts	2,562		3,340
Total assets	2,587		3,373
Liabilities at fair value
Derivative contracts	0		0
Total liabilities	0		0
Net assets (liabilities)	2,587		3,373
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Stocks
Assets at fair value
Nuclear decommissioning trusts	1,559		2,031
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Fixed income
Assets at fair value
Nuclear decommissioning trusts	977		703
Southern California Edison | Fair Value, Measurements, Recurring | Level 1 | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	26		606
Southern California Edison | Fair Value, Measurements, Recurring | Level 2
Assets at fair value
Derivative contracts	0		0
Other	0		0
Nuclear decommissioning trusts	1,857		1,516
Total assets	1,857		1,516
Liabilities at fair value
Derivative contracts	46		86
Total liabilities	46		86
Net assets (liabilities)	1,811		1,430
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	1,745		1,350
Southern California Edison | Fair Value, Measurements, Recurring | Level 2 | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	112		166
Southern California Edison | Fair Value, Measurements, Recurring | Level 3
Assets at fair value
Derivative contracts	269		321
Other	0		0
Nuclear decommissioning trusts	0		0
Total assets	269		321
Liabilities at fair value
Derivative contracts	1,362		1,223
Total liabilities	1,362		1,223
Net assets (liabilities)	(1,093)		(902)
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
Southern California Edison | Fair Value, Measurements, Recurring | Total
Assets at fair value
Derivative contracts	269		321
Other	25		33
Nuclear decommissioning trusts	4,419		4,856
Total assets	4,713		5,210
Liabilities at fair value
Derivative contracts	1,373		1,248
Total liabilities	1,373		1,248
Net assets (liabilities)	3,340		3,962
Southern California Edison | Fair Value, Measurements, Recurring | Total | Stocks
Assets at fair value
Nuclear decommissioning trusts	1,559		2,031
Southern California Edison | Fair Value, Measurements, Recurring | Total | Fixed income
Assets at fair value
Nuclear decommissioning trusts	2,722		2,053
Southern California Edison | Fair Value, Measurements, Recurring | Total | Short-term investments, primarily cash equivalents
Assets at fair value
Nuclear decommissioning trusts	$ 138		$ 772