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Investment Securities and Certificates of Deposit - Additional Information (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Schedule Of Marketable Securities [Line Items]      
Other Payables to Broker-Dealers and Clearing Organizations   $ 99,983  
Certificates of Deposit, at Carrying Value $ 141,218 0  
Certificates of Deposit      
Schedule Of Marketable Securities [Line Items]      
Cash and Cash Equivalents Maturity 4 months    
Debt Securities [Member]      
Schedule Of Marketable Securities [Line Items]      
Investment Securities, Realized Gains (Losses) $ (11) 75 $ (14)
Equity Securities [Member]      
Schedule Of Marketable Securities [Line Items]      
Investment Securities, Realized and Unrealized Gains (Losses) 1,156 95 243
Debt Securities Carried by Broker-Dealers [Member]      
Schedule Of Marketable Securities [Line Items]      
Investment Securities, Realized and Unrealized Gains (Losses) 6 (1,216) 491
Debt Securities, Trading 784,842 550,026  
Debt Securities Carried by Broker-Dealers [Member] | US Treasury Bill Securities [Member]      
Schedule Of Marketable Securities [Line Items]      
Debt Securities, Trading   99,983  
Investment Funds [Member]      
Schedule Of Marketable Securities [Line Items]      
Investment Securities, Realized and Unrealized Gains (Losses) $ 29,025 $ 16,913 $ 13,785