Debt - Extinguishment (Details) (Uncollateralized Debt [Member], USD $)
In Millions, unless otherwise specified
0 Months Ended
Apr. 13, 2015
Notes due 2016 2.75% Interest [Member]  
Extinguishment of Debt [Line Items]  
Extinguishment of Debt, Amount $ 626
Extinguishment of Debt, Gain (Loss), Net of Tax (14)
Basis Points Added To Treasury Rate 0.30%
Notes due 2019 8.5% Interest [Member]  
Extinguishment of Debt [Line Items]  
Extinguishment of Debt, Amount 329
Extinguishment of Debt, Gain (Loss), Net of Tax $ (51)
Basis Points Added To Treasury Rate 0.50%