Cash, Cash Equivalents and Marketable Securities (Details 1) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Gross unrealized gains and losses and fair values
Cost	$ 1,631
Gross Unrealized Gains	2
Gross Unrealized Losses	0
Fair Value	1,633
U.S. treasury and agency obligations [Member]
Gross unrealized gains and losses and fair values
Cost	1,215	1,953
Gross Unrealized Gains	1	2
Gross Unrealized Losses	0	(5)
Fair Value	1,216	1,950
Corporate bonds [Member]
Gross unrealized gains and losses and fair values
Cost	416
Gross Unrealized Gains	1
Gross Unrealized Losses	0
Fair Value	$ 417