Master Netting and Similar Agreements—Repurchase, Reverse Repurchase, and Securities Borrowing Transactions - Securities Sold Under Agreements To Repurchase And Collateral Pledged By Company (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Securities Sold under Agreements to Repurchase [Abstract]
Gross amounts of recognized liabilities	$ 1,158,994	$ 716,925
Gross amounts offset in the Balance Sheets	0	0
Net amounts of liabilities presented in the Balance Sheets	1,158,994	716,925
Offsetting securities purchased under agreements to resell	(70)	(21,004)
Securities/ government guaranteed loans collateral	(1,158,791)	(695,879)
Net amount	$ 133	$ 42