Valuation of debt and equity investments and certain liabilities (Fair value assets and liabilities measured on recurring basis) (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Money market funds	$ 506		$ 167
Corporate obligations	466		693
U.S. government agency and Treasury securities	1,143		1,936
Auction-rate securities	208		280
Mutual funds	158		139
Total assets	2,481		3,215
Contingent consideration			8	[1]
Deferred compensation	180	[1]	159	[1]
Total liabilities	180	[1]	167	[1]
Level 1 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Money market funds	506		167
Corporate obligations	0		0
U.S. government agency and Treasury securities	380		1,120
Auction-rate securities	0		0
Mutual funds	158		139
Total assets	1,044		1,426
Contingent consideration			0	[1]
Deferred compensation	180	[1]	159	[1]
Total liabilities	180	[1]	159	[1]
Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Money market funds	0		0
Corporate obligations	466		693
U.S. government agency and Treasury securities	763		816
Auction-rate securities	0		23
Mutual funds	0		0
Total assets	1,229		1,532
Contingent consideration			0	[1]
Deferred compensation	0	[1]	0	[1]
Total liabilities	0	[1]	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	208		257
Mutual funds	0		0
Total assets	208		257
Contingent consideration			8	[1]
Deferred compensation	0	[1]	0	[1]
Total liabilities	$ 0	[1]	$ 8	[1]

[1] The liabilities above are a component of Accrued expenses and other liabilities or Deferred credits and other liabilities on our balance sheets, depending on the expected timing of payment.