Cash, Cash Equivalents, and Marketable Securities Restricted Cash (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash, Cash Equivalents, and Marketable Securities [Abstract]
Total cash and cash equivalents	$ 25,971	$ 17,504
Restricted cash	189	175
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations	0	62
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 26,160	$ 17,741	$ 21,019	$ 16,907