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Investment Securities - Additional Information (Detail)
12 Months Ended
Dec. 31, 2021
USD ($)
investmentSecurity
Dec. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Investment Securities [Line Items]      
Credit loss $ 0 $ 0 $ 0
Allowance for credit loss 0 0  
Proceeds from sale of available for sale securities 0 229,000 127,066,000
Gain on sale of investment securities 0 7,000 $ 110,000
Realized gain   7,000  
Securities pledged as collateral 423,892,000 $ 429,049,000  
Residential real estate mortgage-backed securities $ 1,254,790,000    
Life of mortgage-backed securities 4 years 10 months 17 days    
Obligations of U.S. government agencies      
Investment Securities [Line Items]      
Available for sale securities in unrealized loss position | investmentSecurity 49    
Percentage of aggregate depreciation in unrealized losses 1.10%    
Obligations of states and political subdivisions      
Investment Securities [Line Items]      
Available for sale securities in unrealized loss position | investmentSecurity 33    
Percentage of aggregate depreciation in unrealized losses 1.38%    
Asset backed securities      
Investment Securities [Line Items]      
Available for sale securities in unrealized loss position | investmentSecurity 35    
Percentage of aggregate depreciation in unrealized losses 0.99%