Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive loss	$ (2,643)	$ (2,309)	$ (2,702)	$ (2,116)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	49	(429)
Other Comprehensive Income (Loss), Before Reclassifications, Tax	7	174
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	3	62
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	59	(193)
Translation Adjustments Other Than Translation Of Balance Sheet Tax Benefit Expense	(17)	51
Pension and other postretirement benefit adjustments, tax cost	20	24
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	(4)	2
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive loss	(1,284)	(895)	(1,332)	(628)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	49	(429)
Other Comprehensive Income (Loss), Before Reclassifications, Tax	(1)	162
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	48	(267)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive loss	(1,360)	(1,424)	(1,379)	(1,492)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	0	0
Other Comprehensive Income (Loss), Before Reclassifications, Tax	6	45
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	13	23
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	19	68
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive loss	1	10	$ 9	$ 4
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	0	0
Other Comprehensive Income (Loss), Before Reclassifications, Tax	2	(33)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(10)	39
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ (8)	$ 6