Shareholders' Equity (Changes in Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			$ (1,746)			$ (1,519)	$ (1,746)	$ (1,519)
Other Comprehensive Income before Reclassifications							35	(170)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax							(8)	(1)
Currency Translation Adjustments	$ (28)			$ (9)			35	(170)
Other Comprehensive Income (Loss)	(20)	$ 30	33	(9)	$ (165)	5	43	(169)
Ending balance	(1,703)			(1,688)			(1,703)	(1,688)
Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(1,724)			(1,484)	(1,724)	(1,484)
Other Comprehensive Income before Reclassifications							35	(170)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax							0	0
Other Comprehensive Income (Loss)								(170)
Ending balance	(1,689)			(1,654)			(1,689)	(1,654)
Defined Benefit Pension
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(14)			(26)	(14)	(26)
Other Comprehensive Income before Reclassifications							0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax							0	(1)
Other Comprehensive Income (Loss)							0	1
Ending balance	(14)			(25)			(14)	(25)
Deferred Loss on Derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			$ (8)			$ (9)	(8)	(9)
Other Comprehensive Income before Reclassifications							0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax							(8)	0
Other Comprehensive Income (Loss)							8	0
Ending balance	$ 0			$ (9)			$ 0	$ (9)