Accumulated Other Comprehensive Loss (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Accumulated other comprehensive loss
Balance at the beginning of the period	$ (782)	$ (583)
Gains (losses) on cash-flow hedges, net of income tax effect of $6 and $13	(14)	26
Amount of losses on cash-flow hedges reclassified to earnings, net of income tax effect of $4 and $6	10	13
Actuarial gains on pension and postretirement obligations, settlements and plan amendments, net of income tax effect of $2	7
Losses related to pension and other postretirement obligations reclassified to earnings, net of income tax effect		1
Currency translation adjustment	(146)	(32)
Balance at end of the period	(925)	(575)
Income tax effect of accumulated other comprehensive gain (loss)
Gains (losses) on cash-flow hedges, income tax effect	(6)	13
Amount of losses on cash flow hedges reclassified to earnings, income tax effect	(4)	(6)
Actuarial gains on pension and postretirement obligations, settlements and plan amendments, income tax effect	2
Accumulated Translation Adjustment
Accumulated other comprehensive loss
Balance at the beginning of the period	(701)	(489)
Currency translation adjustment	(146)	(32)
Balance at end of the period	(847)	(521)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Accumulated other comprehensive loss
Balance at the beginning of the period	(19)	(40)
Gains (losses) on cash-flow hedges, net of income tax effect of $6 and $13	(14)	26
Amount of losses on cash-flow hedges reclassified to earnings, net of income tax effect of $4 and $6	10	13
Balance at end of the period	(23)	(1)
Income tax effect of accumulated other comprehensive gain (loss)
Gains (losses) on cash-flow hedges, income tax effect	(6)	13
Amount of losses on cash flow hedges reclassified to earnings, income tax effect	(4)	(6)
Accumulated Defined Benefit Plans Adjustment
Accumulated other comprehensive loss
Balance at the beginning of the period	(61)	(53)
Actuarial gains on pension and postretirement obligations, settlements and plan amendments, net of income tax effect of $2	7
Losses related to pension and other postretirement obligations reclassified to earnings, net of income tax effect		1
Balance at end of the period	(54)	(52)
Income tax effect of accumulated other comprehensive gain (loss)
Actuarial gains on pension and postretirement obligations, settlements and plan amendments, income tax effect	2
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated other comprehensive loss
Balance at the beginning of the period			(1)	(1)
Balance at end of the period	$ (1)	$ (1)	$ (1)	$ (1)