v2.4.0.6
Assets Measured at Fair Value on Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $)
In Millions, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total cash equivalents and marketable securities $ 9,620 $ 3,398
Money Market Funds
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 944 892
US Government Securities
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 517 60
Marketable Securities 5,557 1,415
US Government Agency Securities
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 69 50
Marketable Securities 2,533 981
Quoted Prices in Active Markets for Identical Assets (Level 1)
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total cash equivalents and marketable securities 9,620 3,398
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money Market Funds
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 944 892
Quoted Prices in Active Markets for Identical Assets (Level 1) | US Government Securities
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 517 60
Marketable Securities 5,557 1,415
Quoted Prices in Active Markets for Identical Assets (Level 1) | US Government Agency Securities
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 69 50
Marketable Securities 2,533 981
Significant Other Observable Inputs (Level 2)
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total cash equivalents and marketable securities 0 0
Significant Other Observable Inputs (Level 2) | Money Market Funds
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 0 0
Significant Other Observable Inputs (Level 2) | US Government Securities
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 0 0
Marketable Securities 0 0
Significant Other Observable Inputs (Level 2) | US Government Agency Securities
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 0 0
Marketable Securities 0 0
Significant Unobservable Inputs (Level 3)
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total cash equivalents and marketable securities 0 0
Significant Unobservable Inputs (Level 3) | Money Market Funds
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 0 0
Significant Unobservable Inputs (Level 3) | US Government Securities
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 0 0
Marketable Securities 0 0
Significant Unobservable Inputs (Level 3) | US Government Agency Securities
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 0 0
Marketable Securities $ 0 $ 0