v2.4.0.6
Valuation of debt and equity investments and certain liabilities (Fair value assets and liabilities measured on recurring basis) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]    
Money market funds $ 55 $ 167
Corporate obligations 294 693
U.S. government agency and Treasury securities 2,121 1,936
Auction-rate securities 134 280
Mutual funds 169 139
Total assets 2,773 3,215
Contingent consideration   8
Deferred compensation 191 159
Total liabilities 191 167
Level 1 [Member]
    
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]    
Money market funds 55 167
Corporate obligations 0 0
U.S. government agency and Treasury securities 606 1,120
Auction-rate securities 0 0
Mutual funds 169 139
Total assets 830 1,426
Contingent consideration   0
Deferred compensation 191 159
Total liabilities 191 159
Level 2 [Member]
    
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]    
Money market funds 0 0
Corporate obligations 294 693
U.S. government agency and Treasury securities 1,515 816
Auction-rate securities 0 23
Mutual funds 0 0
Total assets 1,809 1,532
Contingent consideration   0
Deferred compensation 0 0
Total liabilities 0 0
Level 3 [Member]
    
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]    
Money market funds 0 0
Corporate obligations 0 0
U.S. government agency and Treasury securities 0 0
Auction-rate securities 134 257
Mutual funds 0 0
Total assets 134 257
Contingent consideration   8
Deferred compensation 0 0
Total liabilities $ 0 $ 8