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Securities - Additional Information (Details)
 3 Months Ended
Mar. 31, 2021
USD ($)
Investment
Mar. 31, 2020
USD ($)
Dec. 31, 2020
USD ($)
Investment
Schedule of Investments [Line Items]      
Federal Home Loan Bank stock, at cost | $ $ 698,984,000 [1]   $ 714,005,000 [2]
Net losses on equity securities | $ $ 483,000 $ 215,000  
Collateralized Mortgage Obligations      
Schedule of Investments [Line Items]      
Number of investment securities designated as having a continuous loss position for twelve months or more     4
Capital Trust Notes      
Schedule of Investments [Line Items]      
Number of investment securities designated as having a continuous loss position for twelve months or more 5   5
Asset-backed Securities      
Schedule of Investments [Line Items]      
Number of investment securities designated as having a continuous loss position for twelve months or more 5   7
Corporate Bonds      
Schedule of Investments [Line Items]      
Number of investment securities designated as having a continuous loss position for twelve months or more 5   3
Municipal Bonds      
Schedule of Investments [Line Items]      
Number of investment securities designated as having a continuous loss position for twelve months or more 1   1
[1] Carrying value and estimated fair value are at cost.
[2] Carrying value and estimated fair value are at cost.