Quarterly report pursuant to Section 13 or 15(d)

Workers' Compensation Claims - Additional Information (Detail)

v3.19.3
Workers' Compensation Claims - Additional Information (Detail) - USD ($)
9 Months Ended 12 Months Ended
Sep. 30, 2019
Dec. 31, 2018
Jun. 30, 2019
Sep. 30, 2018
Jun. 30, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Worker's compensation risk claim maximum $ 5,000,000          
Surety bonds 15,000,000          
Balance in Chubb trust accounts 380,600,000 $ 451,000,000        
Collateral securities maintain to cover potential workers compensation claims losses 74,800,000 85,200,000        
Surety bonds and standby letters of credit 74,800,000          
Estimated future liability for unsettled workers' compensation 430,046,000 413,397,000 $ 430,736,000 $ 398,838,000 $ 390,814,000 $ 363,517,000
Reserves incurred in excess of retention limits 3,000,000 3,200,000        
Other Assets [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Accrual for costs incurred in excess of retention limits offset by a receivable 3,000,000 $ 3,200,000        
Wells Fargo Bank, National Association [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Letter of credit 63,700,000          
Maryland [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Reinsurance coverage 1,000,000          
Colorado [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Reinsurance coverage 2,000,000          
California [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Surety bonds and standby letters of credit $ 55,600,000