Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Cash and due from banks	$ 23,197	$ 17,448
Securities purchased under agreements to resell	762	227
Total cash and cash equivalents	$ 23,959	$ 17,675