Financial Instruments Owned and Pledged as Collateral at Fair Value, Securities Purchased Under Agreements to Resell and Securities Sold Under Agreements to Repurchase - Summary of Assets, Liabilities and Collateral Received or Pledged (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial Instruments Owned and Pledged as Collateral at Fair Value	$ 0	$ 12,431
Securities Purchased Under Agreements to Resell	0	13,566
Securities Sold Under Agreements to Repurchase	0	(26,000)
Asset (Liability) Balance [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial Instruments Owned and Pledged as Collateral at Fair Value	0	12,431
Securities Purchased Under Agreements to Resell	0	13,566
Total Assets		25,997
Securities Sold Under Agreements to Repurchase	$ 0	(26,000)
Market Value of Collateral Received or (Pledged) [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Securities Purchased Under Agreements to Resell		13,572
Securities Sold Under Agreements to Repurchase		$ (25,992)