Investments - Carrying Value of Equity Investments Without Readily Determinable Fair Values (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Equity Securities without Readily Determinable Fair Value [Roll Forward]
Carrying value, beginning of period	$ 137	$ 872
Additions	200	23
Sales	0	(718)
Downward adjustments for observable price changes and impairment	0	(20)
Foreign currency translation and other	0	(20)
Carrying value, end of period	$ 337	$ 137