v2.4.0.6
Debt Obligations (Changes in Liability and Equity Components of Convertible Senior Notes) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 12 Months Ended
Mar. 31, 2013
Dec. 31, 2012
Debt Instrument [Line Items]    
Net Carrying Amount $ 1,966 $ 1,976
Equity Component [Member]
   
Debt Instrument [Line Items]    
Gross Equity Component 71 71
Deferred Taxes 32 32
Net Equity Component 39.0 39.0
Liability Component [Member]
   
Debt Instrument [Line Items]    
Principal Balance 93.0 93.0
Unamortized Debt Discount 1 2
Net Carrying Amount 92 91
Accretion of debt discount, Unamortized Debt Discount (1)  
Accretion of debt discount, Net Carrying Amount $ 1