Financial Instruments (Measurement Alternative Investments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Gains and Losses on Marketable and Non-Marketable Equity Securities
Net gain (loss) on equity securities sold during the period	$ 171	$ 42
Net unrealized gain (loss) on equity securities held as of the end of the period	(985)	1,041
Total gain (loss) recognized in other income (expense), net	(814)	1,083
Total unrealized gain (loss) for non-marketable equity securities	$ (948)	$ 390