Quarterly report pursuant to Section 13 or 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 [Member], USD $)
In Millions, unless otherwise specified
Mar. 31, 2014
Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments $ 1,207 $ 709
Marketable securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 1,089 580
Marketable securities | U.S. government and agency debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 354 354
Marketable securities | Mortgage and asset-backed debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 77 75
Marketable securities | Corporate debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 654 146
Marketable securities | Other debt and equity securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 4 5
Other Long-term Investments
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 118 129
Fair Value, Inputs, Level 1
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 373 372
Fair Value, Inputs, Level 1 | Marketable securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 354 353
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 354 353
Fair Value, Inputs, Level 1 | Marketable securities | Mortgage and asset-backed debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
Fair Value, Inputs, Level 1 | Marketable securities | Corporate debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
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 0 0
Fair Value, Inputs, Level 1 | Other Long-term Investments
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 19 19
Fair Value, Inputs, Level 2
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 735 227
Fair Value, Inputs, Level 2 | Marketable securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 735 227
Fair Value, Inputs, Level 2 | Marketable securities | U.S. government and agency debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 1
Fair Value, Inputs, Level 2 | Marketable securities | Mortgage and asset-backed debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 77 75
Fair Value, Inputs, Level 2 | Marketable securities | Corporate debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 654 146
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 4 5
Fair Value, Inputs, Level 2 | Other Long-term Investments
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
Fair Value, Inputs, Level 3
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 99 110
Fair Value, Inputs, Level 3 | Marketable securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
Fair Value, Inputs, Level 3 | Marketable securities | U.S. government and agency debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
Fair Value, Inputs, Level 3 | Marketable securities | Mortgage and asset-backed debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
Fair Value, Inputs, Level 3 | Marketable securities | Corporate debt securities
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
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 0 0
Fair Value, Inputs, Level 3 | Other Long-term Investments
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments $ 99 $ 110