Quarterly report pursuant to Section 13 or 15(d)

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

v3.10.0.1
Workers' Compensation Claims - Summarizes Aggregate Workers' Compensation Reserve Activity (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Workers Compensation Reserve [Abstract]        
Workers’ compensation claims liabilities, Beginning balance $ 390,814 $ 330,079 $ 363,517 $ 312,537
Add: claims expense accrual        
Current period 37,784 39,316 116,803 112,469
Prior periods (2,327) (280) (2,333) 4,984
Total expense accrual 35,457 39,036 114,470 117,453
Less: claim payments related to        
Current period 7,502 6,082 13,783 11,362
Prior periods 19,905 18,466 65,296 67,928
Total paid 27,407 24,548 79,079 79,290
Add: Change in claims incurred in excess of retention limits (26) 118 (70) (6,015)
Workers' compensation claims liabilities, Ending balance 398,838 344,685 398,838 344,685
Incurred but not reported (IBNR) $ 246,174 $ 177,166 $ 246,174 $ 177,166
Ratio of IBNR to workers' compensation claims liabilities 62.00% 51.00% 62.00% 51.00%