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Fair Value of Financial Investments and Liabilities - Recurring Fair Value Measurements (Detail) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2012
Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments, fair value disclosure $ 95 $ 112
Recurring investments [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments, fair value disclosure 22 22
Auction rate securities [Member] | Recurring investments [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments, fair value disclosure 22 22
Assets at Fair Value (Level 3) [Member] | Recurring investments [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments, fair value disclosure 22 22
Assets at Fair Value (Level 3) [Member] | Auction rate securities [Member] | Recurring investments [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments, fair value disclosure $ 22 $ 22