Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Cash and due from banks	$ 17,447,916	$ 6,492,443
Securities purchased under agreements to resell	226,847	289,340
Total cash and cash equivalents	$ 17,674,763	$ 6,781,783