Non-Marketable Investments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments, All Other Investments [Abstract]
Equity method investments	$ 1,700	$ 1,600
Loss on equity method investments	202	227	$ 48
Cost method investments	3,000	2,600
Fair value of cost method investments	8,100	7,500
Variable Interest Entity [Line Items]
Cost of non-marketable debt securities	1,100	1,000
VIE, Not Primary Beneficiary, Aggregated Disclosure
Variable Interest Entity [Line Items]
Net assets of VIE	1,200	1,300
Maximum loss exposure	$ 1,200	$ 1,300