Annual report pursuant to Section 13 and 15(d)

Retirement and Long-Term Incentive Plans - Additional Information (Detail)

v3.3.1.900
Retirement and Long-Term Incentive Plans - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Employer discretionary contribution $ 2,300,000 $ 2,600,000 $ 2,700,000  
Available shares for future issuance 1,345,887,000      
Total unrecognized compensation costs $ 3,000,000      
Recognition of compensation cost weighted average period 3 years 7 months 6 days      
Total fair value of shares vested $ 600,000      
Share-based compensation cost charged against income 2,707,000 1,139,000 672,000  
Total income tax benefit under share-base compensation 0 49,000 116,000  
Incentive Plans        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation cost charged against income $ 2,700,000 $ 1,100,000 $ 700,000  
Employee Stock Option        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of shares authorized 1,000,000      
Employee Stock Option | Long Term Incentive Plan 2002        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of shares authorized 500,000      
Employee Stock Option | Long Term Incentive Plan 2011        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of shares authorized 500,000      
Employee Stock Option | Long Term Incentive Plan 2015        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of shares authorized 1,000,000      
Non Performance Based        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted stock vesting period minimum 3 years      
Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of share awards 262,964.000 107,840 178,950 143,150
Restricted Stock | Non-employee directors        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted stock vesting period 6 months      
Performance Shares        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of share awards   0    
Performance based share compensation expense $ 1,100,000 $ 0 $ 0  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested $ 2,700,000      
Maximum | Employee Stock Option        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Options available for grant to an individual, shares 400,000      
Maximum | Employee Stock Option | Long Term Incentive Plan 2002        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Options available for grant to an individual, shares 200,000      
Maximum | Employee Stock Option | Long Term Incentive Plan 2011        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Options available for grant to an individual, shares 200,000      
Maximum | Employee Stock Option | Long Term Incentive Plan 2015        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Options available for grant to an individual, shares 200,000      
Options available for grant to an outside director, shares 25,000      
2015 Awards        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Performance period awards are earned 2 years      
2016 Awards        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Performance period awards are earned 3 years