Cash, Cash Equivalents and Marketable Securities (Details 2) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	$ 4,243	$ 4,058
Level 1 [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	2,833	3,169
Level 1 [Member] | Cash [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	110	103
Level 1 [Member] | Bank Deposits [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	1,531	455
Level 1 [Member] | Money market funds [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	262	641
Level 1 [Member] | U.S. treasury and agency obligations [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	917	1,950
Level 1 [Member] | Commercial Paper [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0	0
Level 1 [Member] | Corporate bonds [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	13	20
Level 1 [Member] | Asset-backed Securities and other [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0
Level 2 [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	1,410	889
Level 2 [Member] | Cash [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0	0
Level 2 [Member] | Bank Deposits [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0	0
Level 2 [Member] | Money market funds [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0	0
Level 2 [Member] | U.S. treasury and agency obligations [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0	0
Level 2 [Member] | Commercial Paper [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	767	782
Level 2 [Member] | Corporate bonds [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	621	107
Level 2 [Member] | Asset-backed Securities and other [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	22
Level 3 [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0	0
Level 3 [Member] | Cash [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0	0
Level 3 [Member] | Bank Deposits [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0	0
Level 3 [Member] | Money market funds [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0	0
Level 3 [Member] | U.S. treasury and agency obligations [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0	0
Level 3 [Member] | Commercial Paper [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0	0
Level 3 [Member] | Corporate bonds [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0	0
Level 3 [Member] | Asset-backed Securities and other [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	0
Cash [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	110	103
Bank Deposits [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	1,531	455
Money market funds [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	262	641
U.S. treasury and agency obligations [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	917	1,950
Commercial Paper [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	767	782
Corporate bonds [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	634	127
Asset-backed Securities and other [Member]
Fair value measurements for investments aggregated by major security type
Fair value measurements for investments aggregated by major security type	$ 22