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Securities - Additional Information (Details) - USD ($)
3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Sep. 30, 2013
Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]        
Debt securities, available-for-sale, allowance for credit loss $ 0      
Available-for-sale securities transferred to held-to-maturity securities     $ 536,000,000.0  
Unrealized net loss on securities transferred from available-for-sale to held-to-maturity, Gross     $ 13,300,000  
Realized gains on the sale of available-for-sale securities 0 $ 0    
Realized losses on the sale of available-for-sale securities 0 $ 0    
Corporate debt securities, callable, amortized cost 57,000,000.0      
Corporate debt securities, callable, estimated fair value 49,000,000.0      
Securities pledged for other debt obligations, at fair value 455,600,000     $ 475,600,000
Reverse Repurchase Agreement        
Debt Securities, Available-for-sale [Line Items]        
Securities pledged for repurchase agreements, at fair value $ 92,600,000     $ 81,400,000