Marketable Securities Contractual Maturity Table (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Proceeds from Sale and Maturity of Marketable Securities [Abstract]
Available-for-sale Securities, Sale Proceeds	$ 663	$ 917	$ 2,100	$ 2,600
Available-for-Sale Securities Classified by Contractual Maturity, Amortized Cost [Abstract]
Due in one year or less, amortized cost	15,379		15,379
Due after one year through five years, amortized cost	1,966		1,966
Total available-for-sale securities with contractual maturities, amortized cost	17,345		17,345
Available-for-Sale Securities Classified by Contractual Maturity, Fair Value [Abstract]
Due in one year or less, fair value	15,381		15,381
Due after one year through five years, fair value	1,965		1,965
Total available-for-sale securities with contractual maturities, fair value	$ 17,346		$ 17,346