v3.3.1.900
Long-Term Debt (Narrative) (Details) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2015
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Schedule of Capitalization, Long-term Debt [Line Items]        
Long-term debt due in U.S. dollars   $ 19,217    
U.S. dollar equivalent at year-end exchange rates of amounts payable in foreign currencies   708    
Portion of long-term debt included in current liability   558 $ 770  
Long-term debt maturing - 2017   2,959    
Long-term debt maturing - 2018   2,967    
Long-term debt maturing - 2019   2,374    
Long-term debt maturing - 2020   1,602    
Additions to long-term debt $ 8,000 8,028 $ 5,731 $ 345
Long Term Financing [Member]        
Schedule of Capitalization, Long-term Debt [Line Items]        
Unused credit lines   $ 400