Other Liabilities and Provisions (Schedule of Capital Lease Obligation Payments) (Details) $ in Millions	Dec. 31, 2017 USD ($)
Capital Lease Obligation [Line Items]
Minimum lease payments due, next twelve months	$ 99
Minimum lease payments due in two years	99
Minimum lease payments due in three years	99
Minimum lease payments due in four years	87
Minimum lease payments due in five years	8
Minimum lease payments due, thereafter	38
Minimum lease payments, total	430
Capital Lease Future Minimum Interest Payments [Member]
Capital Lease Obligation [Line Items]
Minimum lease payments due, next twelve months	20
Minimum lease payments due in two years	15
Minimum lease payments due in three years	10
Minimum lease payments due in four years	4
Minimum lease payments due in five years	2
Minimum lease payments due, thereafter	5
Minimum lease payment, amount representing interest	56
Capital Lease Present value of Expected Future Payments [Member]
Capital Lease Obligation [Line Items]
Minimum lease payments due, next twelve months	79
Minimum lease payments due in two years	84
Minimum lease payments due in three years	89
Minimum lease payments due in four years	83
Minimum lease payments due in five years	6
Minimum lease payments due, thereafter	33
Minimum lease payments, present value	$ 374