Accrued Payroll and Benefit Costs - Accrued Payroll/Benefit Costs and Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Payroll and benefits	$ 449,246	$ 311,169
Payroll taxes	16,820	18,996
Workers’ compensation	74,117	67,712
Accrued payroll and benefit costs	540,183	397,877
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Applicable payroll taxes deferred	51,100	$ 102,200
Accrued Payroll and Benefits Costs
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Applicable payroll taxes deferred	$ 51,100