Quarterly report pursuant to Section 13 or 15(d)

Workers' Compensation Claims - Additional Information (Detail)

v3.21.1
Workers' Compensation Claims - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Mar. 31, 2021
Jun. 30, 2020
Dec. 31, 2020
Jun. 29, 2020
Mar. 31, 2020
Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Worker's compensation risk claim maximum $ 3,000,000.0 $ 5,000,000.0        
Balance in Chubb trust accounts 295,400,000   $ 290,700,000 $ 115,700,000    
Collateral securities maintain to cover potential workers compensation claims losses 65,200,000   60,100,000      
Surety bonds and standby letters of credit 65,200,000          
Estimated future liability for unsettled workers' compensation 362,663,000   357,746,000   $ 445,310,000 $ 438,986,000
Reserves incurred in excess of retention limits 2,500,000   2,900,000      
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 2,500,000   $ 2,900,000      
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 1,000,000.0 1,000,000.0        
Colorado [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Reinsurance coverage 2,000,000.0 $ 2,000,000.0        
California [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Surety bonds and standby letters of credit $ 39,200,000