Quarterly report pursuant to Section 13 or 15(d)

Workers' Compensation Claims - Summarizes Aggregate Workers' Compensation Reserve Activity (Detail)

v3.8.0.1
Workers' Compensation Claims - Summarizes Aggregate Workers' Compensation Reserve Activity (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Workers Compensation Reserve [Abstract]    
Workers’ compensation claims liabilities, Beginning balance $ 363,517 $ 312,537
Add: claims expense accrual    
Current period 39,052 35,275
Prior periods (6) 2,914
Total expense accrual 39,046 38,189
Less: claim payments related to    
Current period 1,133 1,132
Prior periods 22,535 23,464
Total paid 23,668 24,596
Add: Change in claims incurred in excess of retention limits (21) 103
Workers' compensation claims liabilities, Ending balance 378,874 326,233
Incurred but not reported (IBNR) $ 217,492 $ 162,760
Ratio of IBNR to workers' compensation claims liabilities 57.00% 50.00%