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Fair Value Measurements - Additional Information (Details) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Realized (gains) losses included in net income, net of premium amortization $ 0 $ 0    
Impaired loans not covered under loss-share agreements 36,990,000 29,606,000    
Allowance for loan losses attributable to restructured loans 176,144,000 52,162,000 $ 49,026,000 $ 46,211,000
Valuation adjustment to mortgage servicing rights 11,726,000 1,836,000 0  
Net gain (loss) resulting from fair value changes of these mortgage loans 12,057,000 1,286,000 $ 4,892,000  
Impaired Loans, Not Covered        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Allowance for loan losses attributable to restructured loans $ 12,845,000 $ 2,258,000