Shareholders' Equity Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (1,610)	$ (1,641)
Other comprehensive (loss) income before reclassifications	131	29
Reclassifications	(40)	2
Ending balance	(1,519)	(1,610)	$ (1,641)
Other Comprehensive Income (Loss), Net of Tax	(91)	(31)	760
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,614)	(1,602)
Other comprehensive (loss) income before reclassifications	130	(12)
Reclassifications	0	0
Ending balance	(1,484)	(1,614)	(1,602)
Other Comprehensive Income (Loss), Net of Tax	130	(12)
Defined Benefit Pension [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	13	(29)
Other comprehensive (loss) income before reclassifications	1	41
Reclassifications	(40)	1
Ending balance	(26)	13	(29)
Other Comprehensive Income (Loss), Net of Tax	(39)	42
Deferred Loss on Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive (loss) income before reclassifications	0	0
Reclassifications	0	1
Other Comprehensive Income (Loss), Net of Tax	0	1
Fair Value Hedging [Member] | Interest Rate Swap [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Deferred (Gain) Loss on Discontinuation of Fair Value Hedge	$ (9)	$ (9)	$ (10)