Pension and Other Post-Employment Benefits (Total Benefit Plan Expense Recognized) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Defined Benefit Plan Expense		$ (1)	$ 1
Defined Contribution Plan Expense	$ 24	25	33
Total Benefit Plans Expense	24	24	34
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Defined Benefit Plan Expense	3	13	14
Total Benefit Plans Expense	$ 3	$ 13	$ 14