Equity Investments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Equity Investments	$ 62	$ 66
Net Income (Loss) from equity investments	$ (3)	$ 2	$ 3
Impairment of equity investments			$ 25