Shareholders' Equity (Changes in Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (1,519)	$ (1,610)
Other Comprehensive Income before Reclassifications	5	63
Reclassifications	0	(20)
Other Comprehensive Income (Loss)	5	43
Ending balance	(1,514)	(1,567)
Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(1,484)	(1,614)
Other Comprehensive Income before Reclassifications	5	63
Reclassifications	0	0
Other Comprehensive Income (Loss)	5	63
Ending balance	(1,479)	(1,551)
Defined Benefit Pension
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(26)	13
Other Comprehensive Income before Reclassifications	0	0
Reclassifications	0	(20)
Other Comprehensive Income (Loss)	0	(20)
Ending balance	(26)	(7)
Deferred Loss on Derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(9)	(9)
Other Comprehensive Income before Reclassifications	0	0
Reclassifications	0	0
Other Comprehensive Income (Loss)	0	0
Ending balance	$ (9)	$ (9)