Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 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%
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
Required deposit equal to approximately one day of claims funding activity	6,500
Amount which plan costs were less than the net premiums paid and owed	41,500
Prepaid health insurance, current	32,500
Premiums owed to United	(71,100)
Benefits costs incurred (reduced) related to run-off	9,000	$ (800)
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	$ (7,600)	$ (14,900)
U.S. Treasury rates that correspond with the weighted average estimated claim payout period (in hundredths)	4.00%	1.50%
Incurred but not paid workers compensation liabilities [Abstract]
Liability for Unpaid Claims and Claims Adjustment Expense, Adjustments			229,408	$ 239,623
Workers' Compensation Expense	$ 15,981	$ 8,373
Workers' Compensation Discount, Changed during period	(3,209)	(1,309)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(12,704)	(14,370)
WorkersCompensationLiabilityNetOfAdminFeesCurrent	48,112	49,429
Workers' Compensation Liability, Noncurrent	181,364	182,888	179,629
Workers' Compensation Liability	229,476	232,317
Workers compensation administrative fees accrued	3,800
Undiscounted accrued workers' compensation costs	$ 252,600	248,000
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
Restricted cash	$ 48,113		49,779
Deposits workers compensation	$ 211,226	190,756	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	$ 582,800		$ 600,400
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,769,652	1,577,837
Northeast [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	492,290	449,925
Southeast [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	238,607	202,201
Central [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	318,792	271,310
Southwest [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	340,412	308,838
West [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	362,980	330,771
Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 16,571	$ 14,792