XML 85 R68.htm IDEA: XBRL DOCUMENT v3.3.1.900
Debt (Details 2) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Sep. 19, 2013
Debt Instrument [Line Items]      
Long-term debt $ 4,119 $ 4,369  
Maximum percentage of outstanding Notes that can be redeemed with net cash proceeds from one or more qualified equity offerings 35.00%    
Percentage of principal repayable to option holders upon certain criteria 101.00%    
Interest expense $ 193 201  
Amortization of the debt discount 6 6  
Unsecured Notes      
Debt Instrument [Line Items]      
Interest payable 38 38  
2021 Notes      
Debt Instrument [Line Items]      
Long-term debt 1,500 1,500 $ 1,500
Interest rate     5.625%
2021 Notes | Fair value measurements using significant other observable inputs (Level 2)      
Debt Instrument [Line Items]      
Fair value of notes 1,571 1,586  
2023 Notes      
Debt Instrument [Line Items]      
Long-term debt 750 750 $ 750
Interest rate     6.125%
2023 Notes | Fair value measurements using significant other observable inputs (Level 2)      
Debt Instrument [Line Items]      
Fair value of notes $ 795 $ 810