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	Jun. 30, 2020	Dec. 31, 2019
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial Instruments Owned and Pledged as Collateral at Fair Value	$ 16,206	$ 12,431
Securities Purchased Under Agreements to Resell	5,144	13,566
Securities Sold Under Agreements to Repurchase	(21,350)	(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	16,206	12,431
Securities Purchased Under Agreements to Resell	5,144	13,566
Total Assets	21,350	25,997
Securities Sold Under Agreements to Repurchase	(21,350)	(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	5,151	13,572
Securities Sold Under Agreements to Repurchase	$ (21,341)	$ (25,992)