Compensation and Benefit Plans (Expense Components) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Total non-service cost		$ (8)
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 32	36
Interest cost	35	41
Expected return on plan assets	(57)	(53)
Amortization of prior service cost	1	1
Amortization of net loss	2	5
Regulatory adjustment (deferred)	2	(3)
Total non-service cost	(17)	(9)
Total expense recognized	15	27
Net loss reclassified	2	3
PBOP Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	9	9
Interest cost	21	24
Expected return on plan assets	(30)	(27)
Amortization of prior service cost	0	(1)
Total non-service cost	(9)	(4)
Total expense	0	5
Southern California Edison
Defined Benefit Plan Disclosure [Line Items]
Total non-service cost	(26)	(9)
Southern California Edison | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	31	35
Interest cost	32	37
Expected return on plan assets	(53)	(50)
Amortization of prior service cost	1	1
Amortization of net loss	1	4
Regulatory adjustment (deferred)	2	(3)
Total non-service cost	(17)	(11)
Total expense recognized	14	24
Net loss reclassified	1	2
Southern California Edison | PBOP Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	9	9
Interest cost	21	24
Expected return on plan assets	(30)	(27)
Amortization of prior service cost	0	(1)
Total non-service cost	(9)	(4)
Total expense	$ 0	$ 5