Workers' Compensation Claims (Tables)

12 Months Ended

Dec. 31, 2019

The following table summarizes the aggregate workers' compensation reserve activity (in thousands):

	Years Ended December 31,
	2019			2018			2017
Beginning balance
Workers' compensation claims liabilities	$	413,397		$	363,517		$	312,537
Add: claims expense accrual
Current period		161,691			162,525			154,091
Prior periods		(13,355	)		(3,846	)		5,159
		148,336			158,679			159,250
Less: claim payments related to
Current period		24,414			23,444			19,537
Prior periods		98,445			85,603			82,573
		122,859			109,047			102,110
Change in claims incurred in excess of retention limits		112			248			(6,160	)
Ending balance
Workers' compensation claims liabilities	$	438,986		$	413,397		$	363,517
Incurred but not reported (IBNR)	$	285,191		$	260,529		$	202,227

Ratio of IBNR to workers' compensation claims liabilities		65	%		63	%		56	%