Compensation and Benefit Plans (Expense Components) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Non-service cost
Total non-service benefit		$ (8)			$ (15)
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 32	36		$ 96	108
Non-service cost
Interest cost	35	41		105	123
Expected return on plan assets	(56)	(53)		(169)	(159)
Settlement costs	0	0	$ 8	0	8
Amortization of prior service cost	1	0		2	2
Amortization of net loss	2	4		6	14
Regulatory adjustment (deferred)	2	(3)		7	(9)
Total non-service benefit	(16)	(11)		(49)	(21)
Total expense recognized	16	25		47	87
Settlement costs after tax			$ 5
Net loss reclassified	2	3		6	8
PBOP Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	10	9		29	27
Non-service cost
Interest cost	21	24		63	72
Expected return on plan assets	(31)	(27)		(91)	(81)
Amortization of prior service cost	0	0		(1)	(2)
Total non-service benefit	(10)	(3)		(29)	(11)
Total expense	0	6		0	16
Southern California Edison
Non-service cost
Total non-service benefit	(26)	(9)		(79)	(27)
Southern California Edison | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	31	35		93	105
Non-service cost
Interest cost	32	37		96	111
Expected return on plan assets	(52)	(50)		(159)	(150)
Amortization of prior service cost	1	0		2	2
Amortization of net loss	1	4		4	12
Regulatory adjustment (deferred)	2	(3)		7	(9)
Total non-service benefit	(16)	(12)		(50)	(34)
Total expense recognized	15	23		43	71
Net loss reclassified	1	1		4	4
Southern California Edison | PBOP Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	10	9		29	27
Non-service cost
Interest cost	21	24		63	72
Expected return on plan assets	(31)	(27)		(91)	(81)
Amortization of prior service cost	0	0		(1)	(2)
Total non-service benefit	(10)	(3)		(29)	(11)
Total expense	$ 0	$ 6		$ 0	$ 16