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Investment Securities - Additional Information (Detail)
9 Months Ended
Sep. 30, 2022
USD ($)
investmentSecurity
Dec. 31, 2021
USD ($)
Investment Securities [Line Items]    
Securities pledged as collateral $ 578,794,000 $ 423,892,000
Residential real estate mortgage-backed securities $ 1,570,291,000  
Life of mortgage-backed securities 6 years 6 months 3 days  
Allowance for credit losses $ 0 $ 0
Obligations of U.S. government agencies    
Investment Securities [Line Items]    
Impairment losses recognized 0  
Allowance for credit losses $ 0  
Number of available for sale securities in unrealized loss position (in investment securities) | investmentSecurity 170  
Percentage of aggregate depreciation in unrealized losses 13.35%  
Obligations of states and political subdivisions    
Investment Securities [Line Items]    
Impairment losses recognized $ 0  
Allowance for credit losses $ 0  
Number of available for sale securities in unrealized loss position (in investment securities) | investmentSecurity 218  
Percentage of aggregate depreciation in unrealized losses 15.02%  
Corporate bonds    
Investment Securities [Line Items]    
Number of available for sale securities in unrealized loss position (in investment securities) | investmentSecurity 6  
Percentage of aggregate depreciation in unrealized losses 4.92%  
Asset backed securities    
Investment Securities [Line Items]    
Impairment losses recognized $ 0  
Allowance for credit losses $ 0  
Number of available for sale securities in unrealized loss position (in investment securities) | investmentSecurity 46  
Percentage of aggregate depreciation in unrealized losses 2.98%  
Non-agency collateralized mortgage obligations    
Investment Securities [Line Items]    
Impairment losses recognized $ 0  
Allowance for credit losses $ 0  
Number of available for sale securities in unrealized loss position (in investment securities) | investmentSecurity 22  
Percentage of aggregate depreciation in unrealized losses 10.95%