Annual report pursuant to Section 13 and 15(d)

Summary of Marketable Securities (Detail)

v2.4.0.6
Summary of Marketable Securities (Detail) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]    
Cost $ 1,232 $ 865
Unrealized Gains 12 33
Unrealized Losses (3) (15)
Estimated Fair Value 1,241 883
Current marketable securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost   701
Unrealized Gains   14
Unrealized Losses   (4)
Estimated Fair Value   711
Current marketable securities | U.S. government and agency debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 184 207
Unrealized Gains 3 1
Unrealized Losses   (2)
Estimated Fair Value 187 206
Current marketable securities | Asset-backed Securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 188 220
Unrealized Gains 4 3
Unrealized Losses (1) (1)
Estimated Fair Value 191 222
Current marketable securities | Corporate debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 835 179
Unrealized Gains 4 5
Unrealized Losses (2) (1)
Estimated Fair Value 837 183
Current marketable securities | U.S. state and local municipal debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 15 33
Estimated Fair Value 15 33
Current marketable securities | Other debt and equity securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 10 62
Unrealized Gains 1 5
Estimated Fair Value 11 67
Non-current marketable securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost   164
Unrealized Gains   19
Unrealized Losses   (11)
Estimated Fair Value   172
Non-current marketable securities | Asset-backed Securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost   79
Unrealized Gains   2
Unrealized Losses   (2)
Estimated Fair Value   79
Non-current marketable securities | U.S. state and local municipal debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost   49
Unrealized Gains   2
Unrealized Losses   (6)
Estimated Fair Value   45
Non-current marketable securities | Common equity securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost   20
Unrealized Gains   14
Estimated Fair Value   34
Non-current marketable securities | Preferred equity securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost   16
Unrealized Gains   1
Unrealized Losses   (3)
Estimated Fair Value   $ 14