Goodwill (Schedule of Goodwill) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Line Items]
Goodwill, Acquired During Period	$ 23
Goodwill, Written off Related to Sale of Business Unit	8
Goodwill [Roll Forward]
Balance at December 31, 2017	2,727
Foreign currency translation adjustments	(2)
Balance at March 31, 2018	2,740
Western Hemisphere
Goodwill [Line Items]
Goodwill, Written off Related to Sale of Business Unit	8
Goodwill [Roll Forward]
Balance at December 31, 2017	1,958
Foreign currency translation adjustments	(21)
Eastern Hemisphere
Goodwill [Line Items]
Goodwill, Acquired During Period	23
Goodwill, Written off Related to Sale of Business Unit	0
Goodwill [Roll Forward]
Balance at December 31, 2017	769
Foreign currency translation adjustments	19
Balance at March 31, 2018	811
Western Hemisphere
Goodwill [Line Items]
Goodwill, Acquired During Period	0
Goodwill [Roll Forward]
Balance at March 31, 2018	$ 1,929