Employee Benefits Schedule of Net Benefit Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Interest cost on benefit obligation	$ 3
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	$ 2	$ 2
Interest cost on benefit obligation	3	4	3
Expected return on plan assets	(2)	(2)	(2)
Amortization of prior service cost	0	1	1
Amortization of net actuarial loss	0	0	1
Net periodic benefit cost	3	5	5
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	17	16	18
Interest cost on benefit obligation	33	33	31
Expected return on plan assets	(42)	(40)	(40)
Amortization of prior service cost	0	0	0
Amortization of net actuarial loss	13	14	20
Net periodic benefit cost	21	23	29
Non Qualified Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0
Interest cost on benefit obligation	1	1	1
Expected return on plan assets	0	0	0
Amortization of prior service cost	0	0	0
Amortization of net actuarial loss	1	1	1
Net periodic benefit cost	$ 2	$ 2	$ 2