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Incentive and Restricted Stock Plan and Dividend Reinvestment Plan - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 19, 2015
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Nonstatutory stock options granted since 2006 (in shares)   0    
Number of shares expired (in shares) 155,500      
Weighted average exercise price of shares expired (in dollars per share) $ 37.86      
Unrecognized compensation expense to be recognized   $ 2.7    
Weighted average compensation expense recognize period   1 year 7 months 26 days    
Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Compensation expense   $ 3.0 $ 2.5 $ 1.7
Tax benefit realized on compensation expense   $ 1.1 $ 0.9 $ 0.6
2014 Stock Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Maximum number of common stock authorized (in shares)   750,000    
Stock plan expiration period   10 years    
Number of nonstatutory stock options outstanding (in shares)   0    
2014 Stock Plan | Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted shares granted (in shares)   90,115 110,643  
2014 Stock Plan | Restricted Stock | Employees and Directors        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted shares granted (in shares)   366,570    
2014 Stock Plan | Restricted Stock | Outside Directors        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted shares granted (in shares)   12,728 15,613 16,142
Awards vesting period   1 year    
LTIP | Time-based and Performance-based Restricted Stocks | Senior Management        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted shares granted (in shares)   77,387 95,030 71,699
LTIP | Time-based Restricted Shares | Senior Management        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted stock award vesting after year two, percent   50.00%    
Restricted stock award vesting after year three, percent   50.00%    
LTIP | Performance-based Restricted Shares | Senior Management        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Awards vesting period   3 years