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Investment Securities and Certificates of Deposit - Additional Information (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Feb. 01, 2020
Apr. 30, 2019
Schedule Of Marketable Securities [Line Items]          
Derivative, Notional Amount         $ 14,815
Margin Deposit Assets         $ 680
Derivative, Gain (Loss) on Derivative, Net $ 59        
Certificates of Deposit, at Carrying Value 214,796 $ 100,000      
Debt Securities [Member]          
Schedule Of Marketable Securities [Line Items]          
Investment Securities, Realized Gains (Losses) (14) (28) $ (38)    
Equity Securities [Member]          
Schedule Of Marketable Securities [Line Items]          
Investment Securities, Realized and Unrealized Gains (Losses) 243 (193) 64    
Debt Securities Carried by Broker-Dealers [Member]          
Schedule Of Marketable Securities [Line Items]          
Investment Securities, Realized and Unrealized Gains (Losses) 491 546 (865)    
Investment Funds [Member]          
Schedule Of Marketable Securities [Line Items]          
Investment Securities, Realized and Unrealized Gains (Losses) $ 13,785 $ (5,113) $ 4,088    
Subsequent Event [Member]          
Schedule Of Marketable Securities [Line Items]          
Derivative, Notional Amount       $ 38,908