Compensation and Benefit Plans (Expense Components) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension and Other Postretirement Benefits
Service cost	$ 169.0
Pension Plans
Pension and Other Postretirement Benefits
Service cost	137.0	$ 139.0
Interest cost	164.0	171.0
Settlement loss	(6.4)
Settlement loss, net of tax	(3.8)
Other	(10.0)	(10.0)	$ (14.0)
Postretirement Benefits Other Than Pensions
Pension and Other Postretirement Benefits
Service cost	31.0	35.0	46.0
Interest cost	86.0	97.0	102.0
Expected return on plan assets	(110.0)	(112.0)	(116.0)
Settlement costs	1.0	2.0	1.0
Amortization of prior service cost	(3.0)	(2.0)	(12.0)
Amortization of net loss	0.0	0.0	3.0
Expense under accounting standards	5.0	20.0	24.0
SCE
Pension and Other Postretirement Benefits
Service cost	164.0
SCE | Pension Plans
Pension and Other Postretirement Benefits
Service cost	129.0	132.0
Interest cost	144.0	150.0
Other	(6.0)	(6.0)	(8.0)
SCE | Postretirement Benefits Other Than Pensions
Pension and Other Postretirement Benefits
Service cost	31.0	34.0	46.0
Interest cost	85.0	97.0	102.0
Expected return on plan assets	(110.0)	(112.0)	(116.0)
Settlement costs	1.0	2.0	1.0
Amortization of prior service cost	(2.0)	(2.0)	(12.0)
Amortization of net loss	0.0	0.0	2.0
Expense under accounting standards	5.0	19.0	23.0
Continuing Operations | Pension Plans
Pension and Other Postretirement Benefits
Service cost	138.0	139.0	142.0
Interest cost	164.0	172.0	170.0
Expected return on plan assets	(212.0)	(220.0)	(233.0)
Settlement costs	6.0	0.0	0.0
Amortization of prior service cost	3.0	4.0	5.0
Amortization of net loss	21.0	27.0	40.0
Expense under accounting standards	120.0	122.0	124.0
Regulatory adjustment (deferred)	(28.0)	(21.0)	(6.0)
Total expense recognized	92.0	101.0	118.0
Continuing Operations | SCE | Pension Plans
Pension and Other Postretirement Benefits
Service cost	133.0	136.0	139.0
Interest cost	149.0	156.0	155.0
Expected return on plan assets	(199.0)	(205.0)	(217.0)
Settlement costs	0.0	0.0	0.0
Amortization of prior service cost	3.0	4.0	5.0
Amortization of net loss	17.0	23.0	35.0
Expense under accounting standards	103.0	114.0	117.0
Regulatory adjustment (deferred)	(28.0)	(21.0)	(6.0)
Total expense recognized	$ 75.0	$ 93.0	$ 111.0