Employee Benefits Schedule of Expected Benefit Payments (Details) $ in Millions	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payments in Year One	$ 46
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	49
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	49
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	49
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	51
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	266
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payments in Year One	39
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	41
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	42
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	43
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	44
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	234
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payments in Year One	5
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	5
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	5
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	4
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	5
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	22
Non Qualified Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payments in Year One	2
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	3
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	2
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	2
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	2
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	$ 10