Income Taxes (Schedule of Unrecognized Tax Benefits Rollforward) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Balance at January 1	$ (188)	$ (98)	$ (150)
(Additions) reductions based on tax positions related to current year	(7)	(54)	(4)
(Additions) for tax positions of prior years	(37)	(40)	(3)
Reductions for tax positions of prior years	5	4	33
Settlements	2	6	19
Expiration of statutes of limitations	2	1	5
Currency translation adjustment	3	(7)	2
Balance at December 31	$ (220)	$ (188)	$ (98)