Annual report pursuant to Section 13 and 15(d)

Investments Measured at Fair Value on a Recurring Basis (Detail)

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Investments Measured at Fair Value on a Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $)
In Millions, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments $ 1,475 $ 1,150
Marketable securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 1,241 883
Marketable securities | U.S. government and agency debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 187 206
Marketable securities | Asset-backed Securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 191 301
Marketable securities | Corporate debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 837 183
Marketable securities | U.S. state and local municipal debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 15 78
Marketable securities | Other debt and equity securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 11 115
Other Long-term Investments
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 234 267
Fair Value, Inputs, Level 1
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 204 247
Fair Value, Inputs, Level 1 | Marketable securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 187 247
Fair Value, Inputs, Level 1 | Marketable securities | U.S. government and agency debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 187 206
Fair Value, Inputs, Level 1 | Marketable securities | Other debt and equity securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments   41
Fair Value, Inputs, Level 1 | Other Long-term Investments
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 17  
Fair Value, Inputs, Level 2
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 1,054 498
Fair Value, Inputs, Level 2 | Marketable securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 1,054 498
Fair Value, Inputs, Level 2 | Marketable securities | Asset-backed Securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 191 222
Fair Value, Inputs, Level 2 | Marketable securities | Corporate debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 837 183
Fair Value, Inputs, Level 2 | Marketable securities | U.S. state and local municipal debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 15 33
Fair Value, Inputs, Level 2 | Marketable securities | Other debt and equity securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 11 60
Fair Value, Inputs, Level 3
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 217 405
Fair Value, Inputs, Level 3 | Marketable securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments   138
Fair Value, Inputs, Level 3 | Marketable securities | Asset-backed Securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments   79
Fair Value, Inputs, Level 3 | Marketable securities | U.S. state and local municipal debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments   45
Fair Value, Inputs, Level 3 | Marketable securities | Other debt and equity securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments   14
Fair Value, Inputs, Level 3 | Other Long-term Investments
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments $ 217 $ 267