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Employee Benefits - Additional Information (Detail)
$ / shares in Units, pure in Millions
 12 Months Ended
Dec. 31, 2018
USD ($)
Installment
$ / shares
shares
Dec. 31, 2017
USD ($)
Installment
$ / shares
shares
Dec. 31, 2016
USD ($)
Installment
$ / shares
shares
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Healthcare benefit expense, net of employee contributions $ 17,800,000 $ 17,400,000 $ 15,200,000
Accrued compensation 27,923,000 25,399,000  
Administration expense related to employee contribution plan 1,700,000 1,600,000 1,300,000
Share-based compensation expense 7,846,000 6,591,000 1,894,000
Unrecognized compensation expense $ 5,000,000    
Compensation cost not yet recognized, period for recognition 1 year 9 months 18 days    
Cost of Sales [Member]      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Workers' compensation expense $ 12,800,000 13,500,000 12,100,000
Share-based compensation expense 846,000 965,000  
Administrative [Member]      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Share-based compensation expense $ 6,549,000 5,055,000 $ 1,894,000
Performance Based Stock Units [Member]      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Restricted stock granted, shares | shares 14,072    
Grant date fair value for restricted stock granted | $ / shares $ 52.15    
Share-based compensation expense $ 1,600,000 $ 2,600,000  
Unrecognized compensation expense $ 200,000    
Compensation cost not yet recognized, period for recognition 3 months 18 days    
Performance Based Awards [Member]      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Restricted stock granted, shares | shares 52,892    
Board of Directors [Member] | Restricted Stock [Member]      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Restricted stock granted, shares | shares 5,000 6,000 9,000
Grant date fair value for restricted stock granted | $ / shares $ 60.65 $ 50.50 $ 34.23
Share-based compensation expense $ 200,000 $ 300,000 $ 300,000
2014 Omnibus Incentive Plan [Member]      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Restricted stock granted, shares | shares 100,000 100,000 100,000
Number of equal installments for common stock | Installment 3 3 3
Number of shares surrendered to satisfy tax withholding obligations | shares 41,000 11,000 32,000
Share based compensation, recognized tax benefits $ 500,000 $ 600,000 $ 300,000
Common stock shares available for issuance | shares 2,400,000    
2014 Omnibus Incentive Plan [Member] | Non-Performance-Based Awards [Member] | Administrative [Member]      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Share-based compensation expense $ 4,000,000 2,700,000 $ 1,600,000
2014 Omnibus Incentive Plan [Member] | Officer [Member] | Performance Shares [Member] | Common Stock [Member]      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Restricted stock granted, shares | shares 2    
Number of equal installments for common stock 0.1    
2014 Omnibus Incentive Plan [Member] | Officer [Member] | Performance Based Awards [Member] | Common Stock [Member]      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Share-based compensation expense $ 2,000,000 1,000,000  
Unrecognized compensation expense $ 2,700,000    
Compensation cost not yet recognized, period for recognition 1 year 7 months 6 days    
Medical IBNR Included in Accrued Compensation [Member]      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Accrued compensation $ 2,300,000 $ 1,800,000