Long-Term Debt and Short-Term Borrowings (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Long-Term Debt    
Long-term debt - excluding current portion - carrying value $ 6,459 $ 6,731
Short-Term Borrowings and Current Portion of Long-Term Debt    
Total short-term borrowings and current portion of long-term debt $ 132 $ 106