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Allowance for Loan and Lease Losses and Reserve for Unfunded Commitments - Additional Information (Details) - USD ($)
 3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Dec. 31, 2020
Loans And Leases Receivable Disclosure [Line Items]          
Increase (Recaptured) in allowance for loan and lease losses $ (1,100,000) $ 10,000,000.0 $ (5,700,000) $ 29,300,000  
Commitments outstanding on troubled debt restructurings 0   0   $ 0
Recorded investment in troubled debt restructurings that subsequently defaulted within twelve months 0 0 0 0  
Reserve for unfunded commitments 1,500,000   1,500,000   $ 1,900,000
Provisions for (credits to) unfunded commitments 79,000 519,000 363,000 1,200,000  
Charge-offs or recoveries related to reserve for unfunded commitments     0 0  
Acquired Impaired Loans          
Loans And Leases Receivable Disclosure [Line Items]          
Increase (Recaptured) in allowance for loan and lease losses 405,000 295,000 2,200,000 2,300,000  
Individually Evaluated For Impairment          
Loans And Leases Receivable Disclosure [Line Items]          
Increase (Recaptured) in allowance for loan and lease losses (1,000,000.0) 768,000 602,000 4,100,000  
Collectively Evaluated For Impairment          
Loans And Leases Receivable Disclosure [Line Items]          
Increase (Recaptured) in allowance for loan and lease losses $ (498,000) $ 8,900,000 $ (4,200,000) $ 23,000,000.0