Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Oct. 01, 2019	Sep. 30, 2019
Health Insurance Costs [Abstract]
Percentage of our health insurance coverage provided by United	87.00%		87.00%
Number of days in advance of the beginning of a reporting quarter United establishes cash funding rates			90 days
Required accumulated cash surplus	$ 9,000		$ 9,000		$ 9,000
Required deposit equal to approximately one day of claims funding activity	6,500		6,500
Prepaid health insurance, current	(6,500)		(6,500)
Amount which plan costs were less than the net premiums paid and owed	(15,500)		(15,500)
Premiums owed to United	(10,800)		(10,800)
Benefits costs incurred (reduced) related to run-off	9,800	$ (10,200)	9,800	$ (10,200)
Workers' Compensation Costs [Abstract]
Company's maximum economic burden for the first layer of claims per occurrence							$ 1,500	$ 1,000
Company's maximum aggregate economic burden for claims in excess of 1 million per policy year							$ 6,000	$ 6,000
Decrease Increase in accrued workers' compensation costs for changes in estimated losses			$ (15,000)	$ (26,800)
U.S. Treasury rates that correspond with the weighted average estimated claim payout period (in hundredths)			4.00%	2.00%
Incurred but not paid workers compensation liabilities [Abstract]
Liability for Unpaid Claims and Claims Adjustment Expense, Adjustments					229,408	$ 239,623
Workers' Compensation Expense			$ 30,980	$ 18,780
Workers' Compensation Discount, Changed during period			(6,465)	(3,501)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid			(26,344)	(27,899)
WorkersCompensationLiabilityNetOfAdminFeesCurrent	48,002	53,317	48,002	53,317
Workers' Compensation Liability, Noncurrent	179,577	173,686	179,577	173,686	179,629
Workers' Compensation Liability	227,579	227,003	227,579	227,003
Workers compensation administrative fees accrued	3,400		3,400
Undiscounted accrued workers' compensation costs			$ 252,600	243,900
Time period incurred claims expected to be paid recorded as restricted cash			1 year
Time period incurred claims expected to be paid included in deposits			Greater than 1 year
ReturnOfExcessClaimFunds			$ 43,400
Restricted cash	48,002		48,002		49,779
Deposits workers compensation	180,982	166,077	$ 180,982	166,077	196,370	$ 185,027
Time period estimate of incurred claim costs to be paid included in short-term liabilities			1 year
Time period estimate of incurred claim costs to be paid included in long term liabilities			Greater than 1 year
Revenue from Contract with Customer [Abstract]
Unbilled	590,600		$ 590,600		$ 600,400
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,585,129	1,432,107	3,354,781	3,009,944
Northeast [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	425,848	388,680	918,138	838,602
Southeast [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	221,329	192,782	459,936	394,985
Central [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	284,920	252,039	603,712	523,350
Southwest [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	307,375	279,936	647,787	588,774
West [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	330,122	304,380	693,102	635,152
Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 15,535	$ 14,290	$ 32,106	$ 29,081