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Employee Benefit Plans - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]      
Severance costs $ 1,600,000 $ 610,000 $ 751,000
Deferred compensation agreements expenses $ 1,200,000 684,000 600,000
Maximum percentage of bonus defer by individual under deferred compensation plan 100.00%    
Deferred compensation plan, discretionary payments $ 0 0 0
Deferred compensation liability $ 18,223,000 12,361,000  
Employer contribution percentage to 401(k) plan 3.00%    
Employer contribution in profit-sharing plan $ 3,200,000 2,800,000 $ 2,800,000
Executive Non-qualified Excess Plan [Member]      
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]      
Deferred compensation liability $ 2,100,000 $ 2,900,000  
Maximum [Member]      
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]      
Maximum percentage of salary defer by individual under deferred compensation plan 75.00%