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