Workers' Compensation Claims - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
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	411,100,000	$ 393,500,000
Collateral securities maintain to cover potential workers compensation claims losses	76,100,000	76,100,000
Surety bonds and standby letters of credit	76,100,000
Estimated future liability for unsettled workers' compensation	445,310,000	438,986,000	$ 422,872,000	$ 413,397,000
Reserves incurred in excess of retention limits	3,200,000	3,300,000
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	3,200,000	$ 3,300,000
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