Financial Instruments (Narrative) (Details)
€ in Millions, $ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2016
USD ($)
contract
Sep. 30, 2015
USD ($)
Sep. 30, 2016
USD ($)
contract
Sep. 30, 2015
USD ($)
Sep. 30, 2016
EUR (€)
contract
Dec. 31, 2015
EUR (€)
Jul. 01, 2015
EUR (€)
Senior Notes 6.125% Due May 2023 [Member] | Senior Notes [Member]              
Derivative [Line Items]              
Long-term debt, gross | €         € 322 € 360 € 360
Designated as Hedging Instrument [Member]              
Derivative [Line Items]              
Recognized gains (losses) on derivative net investment hedge, less than $ (6) $ 1 $ (9) $ 1      
Foreign currency forward contracts [Member]              
Derivative [Line Items]              
Number of forward exchange currency contracts | contract 61   61   61    
Derivative notional value $ 444   $ 444        
Foreign currency forward contracts [Member] | Not Designated as Hedging Instrument [Member] | Other Income [Member]              
Derivative [Line Items]              
Derivative gain $ (2) $ 66 $ (2) $ 78