Accumulated Other Comprehensive Loss By Equity Component (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Loss
Balance at the beginning of the period	$ (1,071)
Gains / (loss) on cash-flow hedges, net of income tax effect of $3 and $6, respectively	5	$ (11)
Amount of losses on cash-flow hedges reclassified to earnings, net of income tax effect of $1 and $3, respectively	3	7
Currency translation adjustment	40	39
Balance at end of the period	(1,023)
Income tax effect of accumulated other comprehensive gain (loss)
Gains / (loss) on cash-flow hedges, net of income tax effect	(3)	6
Amount of losses on cash flow hedges reclassified to earnings, income tax effect	(1)	(3)
Cumulative Translation Adjustment
Accumulated Other Comprehensive Loss
Balance at the beginning of the period	(1,008)	(1,025)
Currency translation adjustment	40	39
Balance at end of the period	(968)	(986)
Deferred Gain/(Loss) on Hedging Activities
Accumulated Other Comprehensive Loss
Balance at the beginning of the period	(7)	(29)
Gains / (loss) on cash-flow hedges, net of income tax effect of $3 and $6, respectively	5	(11)
Amount of losses on cash-flow hedges reclassified to earnings, net of income tax effect of $1 and $3, respectively	3	7
Balance at end of the period	1	(33)
Income tax effect of accumulated other comprehensive gain (loss)
Gains / (loss) on cash-flow hedges, net of income tax effect	(3)	6
Amount of losses on cash flow hedges reclassified to earnings, income tax effect	1
Pension Postretirement Adjustment
Accumulated Other Comprehensive Loss
Balance at the beginning of the period	(56)	(47)
Balance at end of the period	(56)	(47)
Unrealized Loss on Investment
Accumulated Other Comprehensive Loss
Balance at the beginning of the period		(1)
Balance at end of the period		(1)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Loss
Balance at the beginning of the period	(1,071)	(1,102)
Gains / (loss) on cash-flow hedges, net of income tax effect of $3 and $6, respectively	5	(11)
Amount of losses on cash-flow hedges reclassified to earnings, net of income tax effect of $1 and $3, respectively	3	7
Currency translation adjustment	40	39
Balance at end of the period	$ (1,023)	$ (1,067)