Other Assets (Schedule of Other Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other Assets [Abstract]
Long-term Investments	$ 26	$ 26
Long-term Receivables	72	71
Deferred Charges and Debt Issuance Costs	7	9
Other	39	32
Other Assets	$ 144	$ 138