Financial Instruments (Schedule of Other Investments Not Readily Marketable) (Details) - Level 3 - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Jan. 31, 2015	Sep. 30, 2015
Other Investments Not Readily Marketable [Roll Forward]
Balance as of December 31, 2014	$ 90	$ 90
Purchases, issuances, and settlements(1)		901
Balance as of September 30, 2015		$ 991
SpaceX
Other Investments Not Readily Marketable [Roll Forward]
Purchases, issuances, and settlements(1)	$ 900