Cash and Cash Equivalents, and Marketable Securities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	$ 8,903	$ 4,907	$ 4,315	$ 3,323
Marketable securities	20,546	13,527
Total cash and cash equivalents, and marketable securities	29,449	18,434
U.S. government securities
Cash, Cash Equivalents and Marketable Securities
Marketable securities	7,130	5,948
U.S. government agency securities
Cash, Cash Equivalents and Marketable Securities
Marketable securities	7,411	4,475
Corporate debt securities
Cash, Cash Equivalents and Marketable Securities
Marketable securities	6,005	3,104
Cash
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	1,364	1,703
Money market funds
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	5,409	2,409
U.S. government securities
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	1,463	597
U.S. government agency securities
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	667	145
Corporate debt securities
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	$ 0	$ 53