Quarterly report pursuant to Section 13 or 15(d)

Summary of Marketable Securities (Detail)

v2.4.0.6
Summary of Marketable Securities (Detail) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]    
Cost $ 593 $ 1,232
Unrealized Gains 11 12
Unrealized Losses 0 (3)
Total Estimated Fair Value 604 1,241
U.S. government and agency debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 189 184
Unrealized Gains 3 3
Unrealized Losses 0 0
Total Estimated Fair Value 192 187
Mortgage and asset-backed debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 181 188
Unrealized Gains 3 4
Unrealized Losses 0 (1)
Total Estimated Fair Value 184 191
Corporate debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 199 835
Unrealized Gains 4 4
Unrealized Losses 0 (2)
Total Estimated Fair Value 203 837
U.S. state and local municipal debt securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 15 15
Unrealized Gains 0 0
Unrealized Losses 0 0
Total Estimated Fair Value 15 15
Other debt and equity securities
    
Schedule of Available-for-sale Securities [Line Items]    
Cost 9 10
Unrealized Gains 1 1
Unrealized Losses 0 0
Total Estimated Fair Value $ 10 $ 11