Annual report pursuant to Section 13 and 15(d)

Share-based Compensation - Additional Information (Detail)

v3.20.4
Share-based Compensation - Additional Information (Detail)
12 Months Ended
Dec. 31, 2020
USD ($)
Plan
Bank
$ / shares
shares
Dec. 31, 2019
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of incentive plans | Plan 2    
Unrecognized compensation expense $ 2,500,000    
Weighted average period cost expected to be recognized 1 year 6 months    
Stock options, expiration term from date of grant 10 years    
Share-based compensation expense $ 2,544,000 $ 3,125,000 $ 3,515,000
Minimum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Period of continuous service 3 years    
Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Period of continuous service 5 years    
2013 Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares of common stock to be granted under equity incentive awards | shares 1,500,000    
Shares available for issuance under the Plan | shares 263,523    
2007 and 2013 Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized compensation expense $ 0    
Options granted in period (shares) | shares 0    
Stock options, expiration term from date of grant 10 years    
2007 and 2013 Plan | Restricted stock awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized compensation expense $ 2,500,000    
Weighted average period cost expected to be recognized 1 year 6 months    
Total fair value of vested shares $ 1,400,000 $ 2,100,000 $ 3,000,000.0
Number of shares granted | shares 125,896 181,204 156,771
Grant date fair value, vested | $ / shares $ 24.68 $ 27.56 $ 27.11
2007 and 2013 Plan | Minimum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Period of continuous service 3 years    
2007 and 2013 Plan | Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Period of continuous service 5 years    
2013 Equity Compensation Plan | Performance Stock Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock options, expiration term from date of grant 3 years    
Total fair value of vested shares $ 271,000    
Number of shares granted | shares 23,937    
Total fair value of granted shares $ 231,000    
Share-based compensation arrangement by share-based payment award, vesting rights Each PSU that vests entitles the recipient to receive one share of the Company’s common stock on a specified issuance date    
Grant date fair value, vested | $ / shares $ 9.65    
Number of regional banks | Bank 51    
Share-based compensation expense $ 32,000