Marketable Securities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended																											12 Months Ended
	Dec. 31, 2009	Dec. 31, 2011 Security	Dec. 31, 2010	Dec. 31, 2011 U.S. government agency securities	Dec. 31, 2010 U.S. government agency securities	Dec. 31, 2011 Foreign government agency securities	Dec. 31, 2010 Foreign government agency securities	Dec. 31, 2011 Corporate debt securities	Dec. 31, 2010 Corporate debt securities	Dec. 31, 2011 U.S. dollar commercial paper	Dec. 31, 2010 U.S. dollar commercial paper	Dec. 31, 2011 Certificates of deposit/time deposits	Dec. 31, 2010 Certificates of deposit/time deposits	Dec. 31, 2011 U.S. treasury securities	Dec. 31, 2010 U.S. treasury securities	Dec. 31, 2011 U.S. municipal securities	Dec. 31, 2010 U.S. municipal securities	Dec. 31, 2011 Asset-backed securities:	Dec. 31, 2010 Asset-backed securities:	Dec. 31, 2011 Asset-backed securities Automobile loan related	Dec. 31, 2010 Asset-backed securities Automobile loan related	Dec. 31, 2011 Asset-backed securities Credit card related	Dec. 31, 2010 Asset-backed securities Credit card related	Dec. 31, 2011 Asset-backed securities Equipment lease related	Dec. 31, 2010 Asset-backed securities Equipment lease related	Dec. 31, 2011 Asset-backed securities Other asset-backed securities	Dec. 31, 2010 Asset-backed securities Other asset-backed securities	Dec. 31, 2011 Auction rate securities D M	Dec. 31, 2010 Auction rate securities
Marketable securities classification
Current marketable securities		$ 1,461	$ 1,101	$ 119	$ 246	$ 8	$ 52	$ 413	$ 280	$ 30	$ 55	$ 49	$ 29		$ 55	$ 9	$ 20	$ 833	$ 364	$ 530	$ 253	$ 244	$ 79	$ 54	$ 24	$ 5	$ 8
Non-current marketable securities		896	540	361	63	15	3	255	192					34	44	5	3	222	228	188	144	24	70	10	14			4	7
Total marketable securities		2,357	1,641
Gross unrealized losses on marketable securities (pre-tax)		12	9																									9	6
Gross unrealized gains on marketable securities (pre-tax)		3	5
Estimated fair value of current and long-term asset-backed securities																		1,055										4	7
Maximum fair market value of asset-backed securities rated AAA/A3 and AAA/A1		7
Number of asset-backed securities rated AAA/A3		1
Number of asset-backed securities rated AAA/A1		1
Number of asset-backed securities not rated AAA or A-1+		2
Percentage of interests in auction rate securities to portfolio, maximum (as a percent)																												1.00%
Minimum period that auction rate securities have been in a loss position (in months)																												12
Pre-determined intervals during which liquidity for auction rate securities is typically provided 1 (in days)																												7
Pre-determined intervals during which liquidity for auction rate securities is typically provided 2 (in days)																												28
Pre-determined intervals during which liquidity for auction rate securities is typically provided 3 (in days)																												35
Pre-determined intervals during which liquidity for auction rate securities is typically provided 4 (in days)																												90
Gross realized losses on sales or maturities of marketable securities	$ 3