Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Cash and due from banks	$ 20,966,421	$ 17,447,916
Securities purchased under agreements to resell	288,438	226,847
Total cash and cash equivalents	$ 21,254,859	$ 17,674,763