Revenue Recognition - Schedule of Revenue Disaggregated by Line of Business (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Revenue from Contract with Customer [Abstract]
Number of reportable segments | segment	3
Guarantee period	90 days
Disaggregation of Revenue [Line Items]
Service revenues	$ 6,461,444	$ 5,109,000	$ 6,074,432
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Service revenues	(580,379)	(239,996)	(172,439)
Accountemps
Disaggregation of Revenue [Line Items]
Service revenues	1,870,563	1,558,024	1,985,221
OfficeTeam
Disaggregation of Revenue [Line Items]
Service revenues	1,058,906	764,947	1,040,755
Robert Half Technology
Disaggregation of Revenue [Line Items]
Service revenues	795,319	695,418	765,831
Robert Half Management Resources
Disaggregation of Revenue [Line Items]
Service revenues	894,334	698,942	792,757
Temporary and consultant staffing
Disaggregation of Revenue [Line Items]
Service revenues	4,038,743	3,477,335	4,412,125
Permanent placement staffing
Disaggregation of Revenue [Line Items]
Service revenues	569,921	370,109	533,432
Risk consulting and internal audit services
Disaggregation of Revenue [Line Items]
Service revenues	$ 1,852,780	$ 1,261,556	$ 1,128,875