Cash, Cash Equivalents and Marketable Securities (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014 security	Dec. 31, 2013 security	Sep. 30, 2013	Dec. 31, 2012
Cash, Cash Equivalents, and Marketable Securities
Cash	$ 1,344	$ 1,044
Money market funds	7,655	2,279
Total cash and cash equivalents	8,999	3,323	3,100	2,384
Total marketable securities	5,251	8,126
Total cash, cash equivalents and marketable securities	14,250	11,449
Number of positions in a continuous loss position for 12 months or longer	0	0
US Government Securities
Cash, Cash Equivalents, and Marketable Securities
Total marketable securities	2,062	5,687
US Government Agency Securities
Cash, Cash Equivalents, and Marketable Securities
Total marketable securities	2,330	2,439
Corporate Debt Securities
Cash, Cash Equivalents, and Marketable Securities
Total marketable securities	$ 859	$ 0