Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

v3.19.3.a.u2
Summary of Significant Accounting Policies - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2019
USD ($)
branch
Segment
shares
Dec. 31, 2018
USD ($)
Dec. 31, 2016
Jan. 24, 2019
shares
Jan. 01, 2019
USD ($)
Financing Receivable, Recorded Investment, Past Due [Line Items]          
Number of reportable segments | Segment 1        
Estimated loss emergence period 2 years 6 months 2 years 6 months 2 years 6 months    
Impairment of intangible assets $ 0        
Goodwill impairment loss 0        
Bank-owned life insurance $ 52,782,000 $ 51,661,000      
Stock options, expiration term from date of grant 10 years        
Number of shares authorized for repurchase (percent)       5.00%  
Number of shares authorized for repurchase under program (shares) | shares       1,500,000  
Shares repurchased $ 7,362,000 $ 36,068,000      
Original opening amount of right-of-use asset $ 36,500,000        
Number of loan and lease segments | Segment 4        
Allowance for loan and lease losses $ 61,400,000        
Leases coverage ratio 1.33%        
ASU 2016-02          
Financing Receivable, Recorded Investment, Past Due [Line Items]          
Original opening amount of right-of-use asset         $ 40,900,000
Stock Repurchase Program          
Financing Receivable, Recorded Investment, Past Due [Line Items]          
Shares repurchased (shares) | shares 375,000        
Shares repurchased $ 7,400,000        
Minimum          
Financing Receivable, Recorded Investment, Past Due [Line Items]          
Period of continuous service 3 years        
Expected allowance for credit losses coverage ratio 1.63%        
Expected allowance for credit losses coverage ratio Increases 22.60%        
Maximum          
Financing Receivable, Recorded Investment, Past Due [Line Items]          
Period of continuous service 5 years        
Expected allowance for credit losses coverage ratio 1.88%        
Expected allowance for credit losses coverage ratio Increases 41.40%        
Split Dollar Death Benefit Agreement          
Financing Receivable, Recorded Investment, Past Due [Line Items]          
Bank-owned life insurance $ 3,900,000        
Full Service          
Financing Receivable, Recorded Investment, Past Due [Line Items]          
Number of branches | branch 35        
Loan Production          
Financing Receivable, Recorded Investment, Past Due [Line Items]          
Number of branches | branch 9