Accrued Payroll and Benefits (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued vacation	$ 46,746	$ 48,976
Accrued payroll and commissions	23,854	23,746
Accrued bonuses	11,101	11,035
Accrued payroll taxes	11,372	11,214
Other accrued benefits	8,633	10,325
Non-U.S. defined contributions and other accrued benefits	7,680	9,722
Total accrued payroll and benefits	$ 109,386	$ 115,018